I've switched to Waterfox (yet another Firefox fork) and so far I'm happy with that choice https://www.waterfox.net/
In a lot of ways, it seems like Waterfox is actually doing a better job of being the type of browser I want than Firefox is anymore; there are a lot more built-in UI customization settings that I'm much more interested in seeing development effort go towards (including some simpler but nice quality of life things like choosing whether to place the tab bar on the top or bottom, or aligning the contents of the URL bar and the tabs either either to the left or to the center, or even whether certain elements should have rounded or square corners) than whatever Mozilla seems to be interested in experimenting with nowadays. Obviously I'm pretty early in my usage, but compared to my expectation that switching over would be either a huge hassle or not really have any immediately obvious differences, I've noticed a number of small but nice changes from my experience with Firefox but not much hassle overall; the only sticking point I currently have is that so far I haven't been able to log into either Gitlab or the webmail site for my custom domain on Namecheap, but I think the former might just be my own error after hitting a limit on two-factor attempts after misunderstanding whether it was asking for my U2F key (which from further research doesn't seem to be supported yet) or an authenticator OTP code, and the latter seems to be getting an error from the server terminating the connection, which is frustrating but feels like it's mostly the fault of the server for apparently not trusting a browser it doesn't recognize (and even seeming to ignoring the user agent when I try to set it to something more "normal"). Given that my Gitlab usage is entirely personal (and mostly just consists of using it as a git server with repos I create using the CLI tool and then don't log into to look at much) and my email also forwards to Gmail (although admittedly with a sometimes annoying delay for stuff like confirmation emails for logins), using a different browser just to access those maybe a couple times a month isn't really going to bother me that much.