I forgot to mention as an alternative to Fastmail, Disroot.org. I have an account with them and it’s functionally very similar to Fastmail and Proton, though their backend is based on Nextcloud and it has that baggage so it may not be your thing. Definitely worth checking out though as it’s free and the only hurdle to signing up is passing a human review (as in, real humans making sure you’re a real human). It’s run by a group of folks who have strong positive positions on privacy and decentralization.

Librewolf is great, and you can self-host Mozilla Sync if you choose to use that feature (Librewolf disables it by default). I know some people prefer Waterfox, and I used it in the past before Librewolf existed; I feel they are both great alternatives to Firefox and far superior to any Chromium-based browser.