I’ve gone between a few but on desktop it’s Librewolf. Just like Firefox but more privacy by default. On Android I’ve tried Fennec, Brave, Iceraven, and Mull. Out of all of them Iceraven has been my favorite simply because of its support for desktop extensions.
Fennec on android, tried mull but it was a bit too hardened, made interacting with apps difficult. It was bromite before that. I keep mulch installed in case fennec has any compatibility issues, but i havent actually had to use it once yet. For desktop, ungoogled chromium does everything i need it to, firefox developer edition is there for back up. I have librewolf installed, but similar to mulch, its just a little too hardened for me to find practical.