If you are a Slack browser user, this userscript will allow you to auto-redirect without Slack asking if you want to open on the desktop app.
- Install a userscript manager as a browser extension like Tampermonkey or Violentmonkey.
- After adding the userscript manager, you can access the userscript raw code and it should show the option to install the userscript.
- You can test the userscript by trying to access a Slack URL.