Asklemmy

Ente Auth is nice for OTPs, it looks nice and I like that it shows the next code in case it's about to switch.

Neo Store for browsing fdroid

Moshidon for Mastodon

Obtainium is pretty good

Seriously guys, no one saying Nextcloud?

• The main app for photo backup.
• Nextcloud Notes for well, notes you can also use from the desktop.
• NC Passwords for well, passwords
• Phonetrack to record your phone to Nextcloud Maps.
• Deck for the Kanban.

Here's a few I enjoy using that I haven't seen mentioned yet:

• Phonograph Plus: elegant music player using Material UI design
• Etar +ICS² : Etar is a nice-looking calendar app that uses Material UI design, and ICS² enables me to sync the Holiday Calendars provided on Thunderbird.net.
• Etar+ DAVx² + NextCloud : enables syncing my local Etar calendar(s) with any NextCloud instance (using CalDAV). DAVx² also allows for syncing my Android contacts to NextCloud (using CardDAV)
• AnySoft Keyboard: extremely customizable, varied keyboard layouts, for those who want all punctuation marks and quote signs built-in.
• Irregular Expressions: alternative keyboard for goofing around with unicode textstyles (🅒🅘🅡🅒🅛🅔🅢, 𝕺𝖑𝖉 𝕰𝖓𝖌𝖑𝖎𝖘𝖍 𝕭𝖔𝖑𝖉, Ｅｘｔｒａ ｗｉｄｅ, etc.)
• Simple Notes : minimalist "note to self" memos.

termux - Terminal and shell, with Linux package environment so you can install and use packages like openssh.

Authenticator Pro. It's like Aegis but supports WearOS devices, so I can get my TOTP codes on my watch instead of having to get my phone out.

FairEmail. One of the best email clients I've used, across any platform. Highly customizable.

Syncthing for syncing photos to my home server.

Readrops for RSS - connects to my FreshRSS server.

Firefox, of course.

Fennec, Bitwarden, Droid-ify, and Tutanota are my essentials I need for life.

I use a few apps from the SimpleMobileTools suite. They aren't full FOSS, they have basic and pro versions where the basic version is GPL3 and the proprietary extended features cost a few bucks. The basic FOSS tools are still decent, if barebones.

The suite includes:

• a calculator
• a phone dialer
• a music player
• a calendar
• a photo gallery (with basic editor)
• an audio recorder
• a flashlight
• a clock
• an app launcher
• an SMS messenger
• a camera
• a keyboard
• a note taker
• a file manager
• a contact book
• a simple painting canvas

I use the gallery and file manager the most. Though admittedly I threw a couple bucks their way for the proprietary extensions. It's not FOSS, but if it was going to be proprietary, I think it's one of the fairest deals in software these days. Better than another bloody subscription model, or holding the ad-free experience hostage behind a paywall.