Self hosting for your own needs is great but you won’t get the “drive by” contributions you get from shared platforms. On GitHub, Gitlab, and Codeberg, if I even see as little as a typo in the readme file, I open a pull request. I will not sign up on a hundred different git hosters for stuff like that.
I’m not sure that an extension would have the necessary access to manipulate the browser like that.
I don’t know if they still do but they used to have. That, however, is something to discuss with the genius decision makers at Mozilla who decide to break extension APIs every couple of years. Firefox on Android still hasn’t recovered from last time.
You only disable the chat. Overall setting seems to be browser.ml.enable.
I like the tab groups.
And nobody should stop you installing an extension that provides tab groups. I agree with the other commentator that some features can be left to extensions and don’t need to be part of the core web browser, though.
Chromium already is open source.