Unexpected import when bundling UMD, broken sourcemap

[decanTyme]

• Version: 3.2.0
• Rollup Version: 3.17.2
• Operating System and version (if applicable): Windows 10 22H2, Build 19045
• Node Version (if applicable): 19.6.0, also tried with 18.14.2
• Does it work with tsc (if applicable): Yes

Reproduction

https://github.com/decanTyme/chartjs-plugin-tailwindcss-colors/tree/rollup-migrate

1. Install deps and run build, should output a dist/plugin.umd.js fine with no warnings
2. Go to rollup.config.mjs and change typescript2 to typescript (there's also some comments there btw)
3. Observe warnings about a util import, a broken sourcemap, and a missing global (which is, again, the rogue util)
4. Optionally, compare both generated bundles, should contain a util import somewhere, which is actually an import of util-deprecate:

// dist/plugin.umd.js

/**
 * For Node.js, simply re-export the core `util.deprecate` function.
 */

var node = require$$0.deprecate; // ??

Expected Behavior

... albeit using rollup-plugin-typescript2, but it is just used for transpiling anyway

Actual Behavior

This is kinda blocking me from using Rollup but TBH, I don't even know which one should be the right ouput. Would really appreciate some insights here tho! 🙂 I would like to keep using rollup-plugin-ts, it fits my needs perfectly, many thanks for this plugin!