You might want to look into Firefox forks—LibreWolf, maybe? Or Seamonkey, which is technically not a Firefox fork but might as well be. I use Pale Moon, but while it does have small tabs and no data collection that I’m aware of (even the code supporting it may have been ripped out in the ongoing efforts to get rid of unwanted maintenanace burdens), it uses the old Firefox extension framework that was deprecated some years ago, so you’d likely have to find alternatives to some extensions.
On the one hand, security is good in the general case, and github has a right to set whatever (legal) conditions they want for the use of their services.
On the gripping hand, for the kind of stuff I’ve put on github in the past? Not worth even a tiny bit of additional friction, especially when I hate git to begin with. I’ve been procrastinating for a while now about moving or deleting existing repositories. Should get on it, I guess.
(There are also certain details of how they’ve executed their security upgrade, which locked some maintainers out of their projects at one point, that I don’t like, and which has reduced my already low trust in them.)