Is there a fork of firefox where you have all the same core functionality and support for extensions but with all the mozilla services (pocket, safe browsing, forced crap on the new tab page, any AI service, etc...) removed?
There are more, those are just the ones I can recall.
Waterfox, Librewolf and Mullvad Browser are worth considering.
Librewolf is nice but breaks a lot of stuff, sites that use webrtc or canvas related things, lots of banking sites refuse to load, and some other issues I can't remember.
https://sizeof.cat/post/web-browser-telemetry-2025-edition/
As for webapps breaking in Librewolf, IME those can be fixed by selectively unblocking canvas (or whatever) for the site in question.