These are what I use:

Browsers: Fennec, LibreWolf

Email Clients: K-9, Fair Email, Proton Mail, Thunderbird

Pictures: Fossify Camera, Fossify Gallery

File Sharing: Proton Drive

YouTube: Tubular

SMS Messaging: Textra (It's not FOSS, but unfortunately there doesn't seem to be a FOSS app in existence that shows the actual name of the person who's sent the message in group chats. They just show an icon, which isn't enough for me to keep track)

App store: Droid-ify (F-Droid), Aurora Store

Password Manager: Bitwarden

eBook Reader: Librera FD

Books: Bookwyrm

Translation: LibreTranslator

Calendar: Proton Calendar

What I can't find good alternatives for:

YouTube itself - enough said

Phone screen translation - I still use Google Assistant, and I'm not aware of anything else that grabs and translates all text on my phone screen

Maps - Rant time. This one is so annoying because there are FOSS navigation apps based on OpenStreetMap that are excellent in every way except one that makes them unusable for me: Using POV navigation instead of observing the convention of up = north. I did find one that lets you maintain a normal map view during navigation, but it doesn't keep your position centered automatically, which makes it impossible to use while driving. I have no idea who all you deranged people are who actually like the POV navigation, but there are definitely a lot of you because I can't find a replacement for Google Maps. I even tried Mapquest because at least it's not Google, but when I tried using it to navigate the first time, it somehow autocorrected "St" to "Ave" and I ended up lost lol. This maps situation really grinds my gears. I do still try to contribute as much as I can to OSM though because it's an important project, and hopefully someday an uninsane developer will make a proper alternative to Google Maps.