The charge isn’t anything to do with validating your passport. They charge you a fee if you want to check in at the airport, cause their checkins are just self service bag drops in most airports, with minimal staff. I’ve flown with Ryanair a lot and never has the phrase “you get what you pay for” felt more apt.
Mull is a decent option on Android that’s fairly similar to Librewolf. You have to manually install the apk though.