diff --git a/packages/mui-base/src/MenuButton/MenuButton.test.tsx b/packages/mui-base/src/MenuButton/MenuButton.test.tsx
index 4a4624f034..a95219f24b 100644
--- a/packages/mui-base/src/MenuButton/MenuButton.test.tsx
+++ b/packages/mui-base/src/MenuButton/MenuButton.test.tsx
@@ -11,10 +11,6 @@ import {
 } from '@base_ui/react/useDropdown';
 import { describeConformanceUnstyled } from '../../test/describeConformanceUnstyled';
 
-// TODO v6: initialize @testing-library/user-event using userEvent.setup() instead of directly calling methods e.g. userEvent.click() for all related tests in this file
-// currently the setup() method uses the ClipboardEvent constructor which is incompatible with our lowest supported version of iOS Safari (12.2) https://github.com/mui/material-ui/blob/master/.browserslistrc#L44
-// userEvent.setup() requires Safari 14 or up to work
-
 const testContext: DropdownContextValue = {
   dispatch: () => {},
   popupId: 'menu-popup',
@@ -146,6 +142,8 @@ describe('<MenuButton />', () => {
             dispatch: dispatchSpy,
           };
 
+          const user = userEvent.setup();
+
           const { getByRole } = render(
             <DropdownContext.Provider value={context}>{buttonComponent}</DropdownContext.Provider>,
           );
@@ -155,7 +153,7 @@ describe('<MenuButton />', () => {
             button.focus();
           });
 
-          await userEvent.keyboard(`{${key}}`);
+          await user.keyboard(`{${key}}`);
 
           expect(dispatchSpy.calledOnce).to.equal(true);
           expect(dispatchSpy.args[0][0]).to.contain({ type: DropdownActionTypes.open });
@@ -171,6 +169,8 @@ describe('<MenuButton />', () => {
             dispatch: dispatchSpy,
           };
 
+          const user = userEvent.setup();
+
           const { getByRole } = render(
             <DropdownContext.Provider value={context}>{buttonComponent}</DropdownContext.Provider>,
           );
@@ -180,7 +180,7 @@ describe('<MenuButton />', () => {
             button.focus();
           });
 
-          await userEvent.keyboard(`{${key}}`);
+          await user.keyboard(`{${key}}`);
 
           expect(dispatchSpy.calledOnce).to.equal(true);
           expect(dispatchSpy.args[0][0]).to.contain({ type: DropdownActionTypes.toggle });
diff --git a/packages/mui-base/src/Select/Select.test.tsx b/packages/mui-base/src/Select/Select.test.tsx
index 57895a72eb..cf7a79fe5a 100644
--- a/packages/mui-base/src/Select/Select.test.tsx
+++ b/packages/mui-base/src/Select/Select.test.tsx
@@ -18,10 +18,6 @@ import { Option, OptionProps, OptionRootSlotProps, optionClasses } from '@base_u
 import { OptionGroup } from '@base_ui/react/OptionGroup';
 import { describeConformanceUnstyled } from '../../test/describeConformanceUnstyled';
 
-// TODO v6: initialize @testing-library/user-event using userEvent.setup() instead of directly calling methods e.g. userEvent.click() for all related tests in this file
-// currently the setup() method uses the ClipboardEvent constructor which is incompatible with our lowest supported version of iOS Safari (12.2) https://github.com/mui/material-ui/blob/master/.browserslistrc#L44
-// userEvent.setup() requires Safari 14 or up to work
-
 describe('<Select />', () => {
   const mount = createMount();
   const { render: internalRender } = createRenderer();
@@ -115,13 +111,16 @@ describe('<Select />', () => {
       const triggerType = selectComponent.props.slots?.root ? 'non-native' : 'native';
       ['Enter', 'ArrowDown', 'ArrowUp', ' '].forEach((key) => {
         it(`opens the dropdown when the "${key}" key is pressed on a ${triggerType} button trigger`, async () => {
+          const user = userEvent.setup();
+
           const { getByRole } = await render(selectComponent);
+
           const select = getByRole('combobox');
           act(() => {
             select.focus();
           });
 
-          await userEvent.keyboard(`{${key}}`);
+          await user.keyboard(`{${key}}`);
 
           expect(select).to.have.attribute('aria-expanded', 'true');
           expect(getByRole('listbox')).not.to.equal(null);
@@ -131,6 +130,8 @@ describe('<Select />', () => {
 
     ['Enter', ' ', 'Escape'].forEach((key) => {
       it(`closes the dropdown when the "${key}" key is pressed`, async () => {
+        const user = userEvent.setup();
+
         const { getByRole } = await render(
           <Select>
             <Option value={1}>1</Option>
@@ -142,7 +143,8 @@ describe('<Select />', () => {
         });
 
         const listbox = getByRole('listbox');
-        await userEvent.keyboard(`{${key}}`);
+
+        await user.keyboard(`{${key}}`);
 
         expect(select).to.have.attribute('aria-expanded', 'false');
         expect(listbox).toBeHidden();
@@ -151,6 +153,8 @@ describe('<Select />', () => {
 
     ['Enter', ' '].forEach((key) => {
       it(`does not close the multiselect dropdown when the "${key}" key is pressed`, async () => {
+        const user = userEvent.setup();
+
         const { getByRole, queryByRole } = await render(
           <Select multiple>
             <Option value={1}>1</Option>
@@ -161,7 +165,7 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard(`{${key}}`);
+        await user.keyboard(`{${key}}`);
 
         expect(select).to.have.attribute('aria-expanded', 'true');
         expect(queryByRole('listbox')).not.to.equal(null);
@@ -171,6 +175,8 @@ describe('<Select />', () => {
     describe('item selection', () => {
       ['Enter', ' '].forEach((key) =>
         it(`selects a highlighted item using the "${key}" key in single mode`, async () => {
+          const user = userEvent.setup();
+
           const { getByRole } = await render(
             <Select>
               <Option value={1}>1</Option>
@@ -180,9 +186,9 @@ describe('<Select />', () => {
 
           const select = getByRole('combobox');
 
-          await userEvent.pointer({ target: select, keys: '[MouseLeft]' });
-          await userEvent.keyboard('{ArrowDown}');
-          await userEvent.keyboard(`{${key}}`);
+          await user.pointer({ target: select, keys: '[MouseLeft]' });
+          await user.keyboard('{ArrowDown}');
+          await user.keyboard(`{${key}}`);
 
           expect(select).to.have.text('2');
         }),
@@ -190,6 +196,8 @@ describe('<Select />', () => {
 
       ['Enter', ' '].forEach((key) =>
         it(`selects a highlighted item using the "${key}" key in multiple mode`, async () => {
+          const user = userEvent.setup();
+
           const { getByRole } = await render(
             <Select multiple>
               <Option value={1}>1</Option>
@@ -199,10 +207,10 @@ describe('<Select />', () => {
 
           const select = getByRole('combobox');
 
-          await userEvent.pointer({ target: select, keys: '[MouseLeft]' });
-          await userEvent.keyboard(`{${key}}`);
-          await userEvent.keyboard('{ArrowDown}');
-          await userEvent.keyboard(`{${key}}`);
+          await user.pointer({ target: select, keys: '[MouseLeft]' });
+          await user.keyboard(`{${key}}`);
+          await user.keyboard('{ArrowDown}');
+          await user.keyboard(`{${key}}`);
 
           expect(select).to.have.text('1, 2');
         }),
@@ -211,6 +219,8 @@ describe('<Select />', () => {
 
     describe('text navigation', () => {
       it('navigate to matched key', async () => {
+        const user = userEvent.setup();
+
         const { getByRole, getByText } = await render(
           <Select>
             <Option value={1}>Apple</Option>
@@ -227,15 +237,17 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('d');
+        await user.keyboard('d');
         expect(getByText('Dragon Fruit')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('r');
+        await user.keyboard('r');
         expect(getByText('Dragon Fruit')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('z');
+        await user.keyboard('z');
         expect(getByText('Dragon Fruit')).to.have.class(optionClasses.highlighted);
       });
 
       it('navigate to next element with same starting character on repeated keys', async () => {
+        const user = userEvent.setup();
+
         const { getByRole, getByText } = await render(
           <Select>
             <Option value={1}>Apple</Option>
@@ -252,11 +264,11 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Cherry')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Calamondin')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Cherry')).to.have.class(optionClasses.highlighted);
       });
 
@@ -275,6 +287,8 @@ describe('<Select />', () => {
           );
         }
 
+        const user = userEvent.setup();
+
         const { getByRole, getByTestId } = await render(
           <Select>
             <RichOption data-testid="1" value={1} label="Apple" />
@@ -291,15 +305,17 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('d');
+        await user.keyboard('d');
         expect(getByTestId('5')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('r');
+        await user.keyboard('r');
         expect(getByTestId('5')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('z');
+        await user.keyboard('z');
         expect(getByTestId('5')).to.have.class(optionClasses.highlighted);
       });
 
       it('skips the non-stringifiable options', async () => {
+        const user = userEvent.setup();
+
         const { getByRole, getByText } = await render(
           <Select>
             <Option value={{ key: 'Apple' }}>Apple</Option>
@@ -319,15 +335,17 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Cherry')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Calamondin')).to.have.class(optionClasses.highlighted);
-        await userEvent.keyboard('c');
+        await user.keyboard('c');
         expect(getByText('Cherry')).to.have.class(optionClasses.highlighted);
       });
 
       it('navigate to options with diacritic characters', async () => {
+        const user = userEvent.setup();
+
         const { getByRole, getByText } = await render(
           <Select>
             <Option value={{ key: 'Aa' }}>Aa</Option>
@@ -343,14 +361,16 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('b');
+        await user.keyboard('b');
         expect(getByText('Ba')).to.have.class(optionClasses.highlighted);
 
-        await userEvent.keyboard('{Control>}{Alt>}ą{/Alt}{/Control}');
+        await user.keyboard('{Control>}{Alt>}ą{/Alt}{/Control}');
         expect(getByText('Bą')).to.have.class(optionClasses.highlighted);
       });
 
       it('navigate to next options with beginning diacritic characters', async () => {
+        const user = userEvent.setup();
+
         const { getByRole, getByText } = await render(
           <Select>
             <Option value={{ key: 'Aa' }}>Aa</Option>
@@ -365,18 +385,20 @@ describe('<Select />', () => {
           select.click();
         });
 
-        await userEvent.keyboard('{Control>}{Alt>}ą{/Alt}{/Control}');
+        await user.keyboard('{Control>}{Alt>}ą{/Alt}{/Control}');
         expect(getByText('ąa')).to.have.class(optionClasses.highlighted);
 
-        await userEvent.keyboard('{Alt>}{Control>}ą{/Control}{/Alt}');
+        await user.keyboard('{Alt>}{Control>}ą{/Control}{/Alt}');
         expect(getByText('ąb')).to.have.class(optionClasses.highlighted);
 
-        await userEvent.keyboard('{Control>}{AltGraph>}ą{/AltGraph}{/Control}');
+        await user.keyboard('{Control>}{AltGraph>}ą{/AltGraph}{/Control}');
         expect(getByText('ąc')).to.have.class(optionClasses.highlighted);
       });
     });
 
     it('closes the listbox without selecting an option when "Escape" is pressed', async () => {
+      const user = userEvent.setup();
+
       const { getByRole, queryByRole } = await render(
         <Select defaultValue={1}>
           <Option value={1}>1</Option>
@@ -390,8 +412,8 @@ describe('<Select />', () => {
         select.click();
       });
 
-      await userEvent.keyboard('{ArrowDown}'); // highlights '2'
-      await userEvent.keyboard('{Escape}');
+      await user.keyboard('{ArrowDown}'); // highlights '2'
+      await user.keyboard('{Escape}');
 
       expect(select).to.have.attribute('aria-expanded', 'false');
       expect(select).to.have.text('1');
@@ -399,6 +421,8 @@ describe('<Select />', () => {
     });
 
     it('closes the listbox after selecting with keyboard', async () => {
+      const user = userEvent.setup();
+
       const { getByRole, queryByRole } = await render(
         <Select defaultValue={1}>
           <Option value={1}>1</Option>
@@ -408,9 +432,9 @@ describe('<Select />', () => {
 
       const select = getByRole('combobox');
 
-      await userEvent.pointer({ target: select, keys: '[MouseLeft]' });
-      await userEvent.keyboard('{ArrowDown}'); // highlights '2'
-      await userEvent.keyboard('{Enter}');
+      await user.pointer({ target: select, keys: '[MouseLeft]' });
+      await user.keyboard('{ArrowDown}'); // highlights '2'
+      await user.keyboard('{Enter}');
 
       expect(select).to.have.attribute('aria-expanded', 'false');
       expect(select).to.have.text('2');
@@ -438,6 +462,8 @@ describe('<Select />', () => {
         return <Option {...props} ref={ref} slotProps={{ root: { style: { height: '50px' } } }} />;
       });
 
+      const user = userEvent.setup();
+
       const { getByRole } = await render(
         <Select slots={{ listbox: SelectListbox }}>
           <CustomOption value="1">1</CustomOption>
@@ -455,23 +481,23 @@ describe('<Select />', () => {
         select.focus();
       });
 
-      await userEvent.keyboard('{ArrowDown}'); // opens the listbox and highlights 1
+      await user.keyboard('{ArrowDown}'); // opens the listbox and highlights 1
 
       const listbox = getByRole('listbox');
 
-      await userEvent.keyboard('{ArrowDown}'); // highlights 2
+      await user.keyboard('{ArrowDown}'); // highlights 2
       expect(listbox.scrollTop).to.equal(0);
 
-      await userEvent.keyboard('{ArrowDown}'); // highlights 3
+      await user.keyboard('{ArrowDown}'); // highlights 3
       expect(listbox.scrollTop).to.equal(50);
 
-      await userEvent.keyboard('{ArrowDown}'); // highlights 4
+      await user.keyboard('{ArrowDown}'); // highlights 4
       expect(listbox.scrollTop).to.equal(100);
 
-      await userEvent.keyboard('{ArrowUp}'); // highlights 3
+      await user.keyboard('{ArrowUp}'); // highlights 3
       expect(listbox.scrollTop).to.equal(100);
 
-      await userEvent.keyboard('{ArrowUp}'); // highlights 2
+      await user.keyboard('{ArrowUp}'); // highlights 2
       expect(listbox.scrollTop).to.equal(50);
     });
   });
@@ -1074,6 +1100,8 @@ describe('<Select />', () => {
     });
 
     it('closes the listbox when the select is clicked again', async () => {
+      const user = userEvent.setup();
+
       const { getByRole } = await render(
         <Select>
           <Option value={1}>One</Option>
@@ -1082,16 +1110,18 @@ describe('<Select />', () => {
 
       const select = getByRole('combobox');
 
-      await userEvent.pointer({ keys: '[MouseLeft]', target: select });
+      await user.pointer({ keys: '[MouseLeft]', target: select });
 
       expect(select).to.have.attribute('aria-expanded', 'true');
 
-      await userEvent.pointer({ keys: '[MouseLeft]', target: select });
+      await user.pointer({ keys: '[MouseLeft]', target: select });
 
       expect(select).to.have.attribute('aria-expanded', 'false');
     });
 
     it('closes the listbox without selecting an option when focus is lost', async () => {
+      const user = userEvent.setup();
+
       const { getByRole, getByTestId } = await render(
         <div>
           <Select defaultValue={1}>
@@ -1111,7 +1141,8 @@ describe('<Select />', () => {
       });
 
       const listbox = getByRole('listbox');
-      await userEvent.keyboard('{ArrowDown}'); // highlights '2'
+
+      await user.keyboard('{ArrowDown}'); // highlights '2'
 
       const focusTarget = getByTestId('focus-target');
       act(() => {
@@ -1285,6 +1316,8 @@ describe('<Select />', () => {
       return <li {...other} ref={ref} />;
     });
 
+    const user = userEvent.setup();
+
     const { getByRole } = await render(
       <Select>
         <Option
@@ -1331,11 +1364,11 @@ describe('<Select />', () => {
     // React renders twice in strict mode, so we expect twice the number of spy calls
     expect(renderOption1Spy.callCount).to.equal(2); // '1' as focusVisible becomes true
 
-    await userEvent.keyboard('{ArrowDown}'); // highlights '2'
+    await user.keyboard('{ArrowDown}'); // highlights '2'
     expect(renderOption1Spy.callCount).to.equal(6); // '1' rerenders as it loses highlight
     expect(renderOption2Spy.callCount).to.equal(4); // '2' rerenders as it receives highlight
 
-    await userEvent.keyboard('{Enter}'); // selects '2'
+    await user.keyboard('{Enter}'); // selects '2'
     expect(renderOption1Spy.callCount).to.equal(6);
     expect(renderOption2Spy.callCount).to.equal(8);
 
diff --git a/test/karma.conf.profile.js b/test/karma.conf.profile.js
index 5bf1104dc9..4482e12b79 100644
--- a/test/karma.conf.profile.js
+++ b/test/karma.conf.profile.js
@@ -153,7 +153,8 @@ module.exports = function setKarmaConfig(config) {
           os: 'Windows',
           os_version: '10',
           browser: 'firefox',
-          browser_version: '15.0',
+          // We support Firefox 115.x per .browserslistrc
+          browser_version: '115.0',
         },
         // No accurate performance timings (integer precision instead of double).
         safari: {