I would second this suggestion, even if you don't consider yourself technically proficient, still give LibreWolf a try because it works out of the box just as well as Firefox for 99% of web pages ime. If you're inclined to fine tune it, it walks you through the tweaks you might want to implement at the beginning.
For mobile I've been using Fennec, which has worked fine if not better than Firefox mobile. But there may be better suggestions out there for a mobile browser.