S Mode is a more locked down mode for Windows. While in S Mode, your PC can only install apps from the Microsoft Store. This means you can only browse the web in Microsoft Edge—you can't install Chrome or Firefox.

Windows 11 in S mode is a version of Windows 11 that's streamlined for security and performance, while providing a familiar Windows experience. To increase security, it allows only apps from Microsoft Store, and requires Microsoft Edge for safe browsing.

https://support.microsoft.com/en-us/windows/windows-10-and-windows-11-in-s-mode-faq-851057d6-1ee9-b9e5-c30b-93baebeebc85

easy peasy once you know how! Thank you!

To keep you using Edge. I'd be really embarrassed if I were them.

You could try downloading Brave browser, which is pretty small and private. Don't swap all your settings over, but use Brave to download Firefox. Around a year ago I ditched Firefox in favour of Waterfox, which is almost the same but less resource hungry and it uses the same add-ons as FF.

I know this seems the long way around, but Brave with DuckDuckGo is a handy little browser and search engine to have as a spare.

Good to know.