Asklemmy

Syncthing.

Allows you to use a laptop and sync your phone to it. No iCloud or Google drive needed. All syncs locally.

Aegis is a FOSS, local only 2 factor TOTP generator. Essentially a Google authenticator without the Google.

AntennaPod. It's easily the best podcast player I've tried, it's open source too which is nice.

KDE Connect (FREE, open source) is definitely a gem. I love using my phone as a remote mouse and keyboard for my HTPC, and syncing clipboard, files, links, and notifications with the other devices I've paired with. (BTW, despite the name, you don't need KDE - or Linux even - to use it. It works on Windows and Android too.)

URLCheck (FREE, open source) is fantastic. It's a little pop-up that appears when you click a link, showing you the full URL and letting you modify it before you open with your browser/associated app (e.g., to remove tracking parameters):

URLCheck acts as an amazingly customizable and powerful intermediary when opening url links, allowing, among other things: to remove trackers, affiliate links, unnecessary elements, check Hosts, facilitating link holding and sharing, protecting against certain phishing techniques and many more...

So I did NewPipe for using YouTube and that's all I have to say on the matter 😘

Smart tube for Android TV.

KISS Launcher. Fast and flexible homescreen replacement that puts quick search first, letting you optionally scroll through an app list.

Ever work on electronics?

I use an apk called "Electrodoc" and it identifies and helps you figure out what all you need for all sorts of transistors and capacitors and smd's and inductors and all that sorts of crap. Has loads of info and pictures and calculations you can punch in for stuff. Super handy.

Aves Libre - Image Viewer

Just tried it 30mins ago. Super slick and feature packed. Available on Fdroid too.

Genius Scan. A shameful exception in my otherwise fully FOSS phone.

It scans multi-page documents with the camera, OCRs them, then uploads them automatically to Nextcloud (or manually to any other app, like Paperless).

Tachiyomi is a brilliant manga reader and tracker. Or you can get its fork, Aniyomi which has anime support and sources as well, not just manga.

Not sure how "hidden" these are, but they can be really useful

"AMdroid" by Smart Alarm Clock Team (Higley-configurable alarm clock with different alarm profiles, options for a post-alarm confirmation, and dismiss challenges)

"Engineering Converter Plus" by thermofluids.net (Has every unit conversion I've ever needed without needing to be online - Free version avaliable)

"Network Analyzer" by Jiri Techet (Good for helping to find the best spot/s for a wireless router or access point)

"Oldschool Editor : Text Editor" by AbhishekPandey (A no nonsense text editor)

"Unseen - No Last Seen" by Firehawk (Good to help look through message spam without alerting the spammer with a read receipt that your account is active)

Phonograph plus if you are a local music nut like me and obtainium if you prefer to not use fdroid to manage your foss app updates

Minimalist phone. If you have ADHD and/or want to increase productivity or get anxiety about your phone notifications, look into this app. It's been sooooo beneficial for me.

MiX

Very good file explorer and server

JINA App Drawer.

My most used app on my device.

Basically lets you swipe up from the home button to reveal a customized grid of apps + app search.

Makes it so:

• I never have to go back to my home screen to launch a new app
• I can use my entire home screen for widgets and to just look nice

Into the breach. One of the best mobile games there is. Sadly you can't get it legally anymore without Netflix subscription.

Just Run Zero to 5K.

For me it's the Golden Age of apps. Easy to use, minimal, good UI, no ads with the ability to buy premium, all the features that you need and non that you don't.

If you want to start jogging I highly recommend it. I think it's perfect.

Edit: I went from barely able to jog an exhausting half mile to jogging 4.5 miles in 13 weeks. It wasn't easy and I think I "failed" a jog twice but having a clear goal with the encouragement of seeing a timer motivate you really helped me.

Oto Music (Play Store link) has been my mp3/offline music player of choice for years now. Stable, pretty, performant, and has tag editing features built in. Still gets updates at least once or twice a year, which is all ya really need for an offline player.

Megalodon (Play Store link) is my Mastodon client of choice, tons of little ease-of-use improvements over the official client. Some people might already be familiar with this if they're on Lemmy, but maybe someone looking for a better Masto client will get something from this.

Buzzkill for control over notifications.

Musicolet is the best audio player I've found.

ResilioSync for synching files between devices (all platforms as far as I know)

Shattered Pixel Dungeon - a pretty good FOSS roguelike, gets updated every month or so. Can be a bit hard to learn and beat the game for the first time but trying to go farther and farther each run is really fun.

Leon, the URL cleaner. Use it to remove tracking links either before opening them or before sharing them.

https://github.com/svenjacobs/leon

Been really impressed with the open-source spending tracking app Cashew

Thumb-key and Auxio (music player)

Voice - Audio book player Minimalistic audio book player that supports folders with ".nomedia". Great if you want to keep your audio books and music library separated.

SpeechCentral, reads almost any text aloud and basically turns anything into an audiobook that follows along (highlights) so you can read and listen at the same time or export audio for hands/eye free listening!

YouTube Revanced Extended - No ads, almost endless customisation options, built in Return Dislikes and Sponsorblock

SmartTube Next - Same thing for Android TV devices

Boost for Lemmy - The best Lemmy client as far as I'm concerned, highly customisable too

AIMP - No nonsense music player with a clear UI

I like Weather Warbler because it's simple. Not perfect, but free, simple, no ads.

Feeder an RSS feed reader. It is amazing, reading all the news I care about without leaving Feeder. It saves me a lot of energy declining cookies. It is available on F-Droid.

Read You, probably the best RSS reader available on Android. The bad: still in beta and no sync with Feedly (yet).

Sync for Lemmy, also the best client for Lemmy in Android by far. Design and user experience are delightful. Bad: ads with an expensive subscription. Good: with adguard DNS ads disappear.