These are some of my essential Android apps. It's a lot, but I couldn't decide which ones are less essential, sorry. All of them are FOSS and can be found on F-Droid or IzzyOnDroid (F-Droid compatible) repos

• Neo Store is my favorite F-Droid client (F-Droid is essential, but the official app sucks IMO)
• Aegis is a great 2FA authentication app
• AirGuard if you think you might be a victim of AirTag stalking
• AShell (requires Shizuku) for ADB access without computer (you need to be on wifi tho)
• CloudStream when you are too broke to afford 10 subscription-based streaming services
• echo unmaintained but I was unable to find any alternative. It records in the background and keeps the last N minutes in memory. You can save last X minutes as mp3 whenever you want.
• feeder is a great RSS reader
• Inner Tune best YT Music client on F-Droid IMO (I tested all of them I could find few weeks ago)
• KDE Connect - connects you Android phone with your PC
• KryptEY might be useful if EU bans encryption
• libretorrent best torrent app on Android I have used
• Translate You translator app supporting many sources
• unexpected keyboard is my favorite for writing terminal commands in Termux or programming
• Voice is the must have for localy downloaded audiobooks
• YTDLnis is very cool yt-dlp GUI full of features + can be set as downloader app in ReVanced settings
• and the best of all: Termux - Linux terminal on your Android
• bonus: zotify (website) is the only Spotify downloader I know about that actually downloads from Spotify (!). It's a command line app. It can be pretty easily installed in Termux though and usage is not very difficult if you are familiar with the command line. Please read the README. I personally love it.

Bitwarden. It doesn't get the fame it deserves.

Termux.

The flexibility of having a Linux system in your pocket is pretty darn remarkable, even though the most common thing I actually do with it is just leave ping running in the background to catch network problems.

Aegis. An open source authenticator app similar to Google Authenticator or Authy. I really like to back up my encrypted credentials to my nextcloud.

I recently found out about URLCheck. You set it as default browser and it gives you a popup when clicking on a link. You can preview, edit the link and open it with the app you want instead of automatically opening it in its default app. Especially useful for apps that don't give a link preview on text like my comment that hide the link address.

I rather like KDE Connect.

I've got some form of open source sensors multitool that gives me the raw data from my phone's sensors. That helps me troubleshoot other sensors at work.

Oh and while not strictly speaking an app itself, I rather like Godot. Within a day I was writing my own android apps (it uses a Python-like scripting language). Mostly stuff to send/receive UDP networking packets to test various systems. So my next favorite android app might be one I write myself ;)

Desmos - free scientific calculator, no ads or fluff.

Organic Maps for offline navigation

Adguard for Android - uses a local VPN to block ads system wide in most apps.

Magisk -> Adguard certificate - moves the Adguard cert to the system store so you can MitM HTTPS traffic and block even more ads (eg: in Chrome, or the system webview)

Magisk -> universal safetynet fix - spoof safetynet and play integrity

Magisk -> ACC - set battery charge cutoffs for devices that don't have an 80/85% charge limit built into the firmware

Obtainium - update open source apps directly from GitHub releases, fdroid repos, https sources by regex, etc

Accubattery - track and estimate device battery wear over time so you know when you're ready to replace one

Zarchiver - handle zstd compressed files on Android

Aegis an open source, cloud free, TOTP application. You can create local backups and everything.

I found this after trying to export my keys from Authy, turns out you can't.

Plantnet - Like Shazam but for plants

Torque is an app that can connect to a cheap Bluetooth plug that goes into your car's OBD2 port. You can set up custom gauge readouts, log data, check engine codes, measure power and torque. It was very useful to me when my car was overheating since I could get a coolant temp read out. Also when my alternator died since I could get a voltage readout.

I'm not sure if they're popular or not but I didn't see them mentioned in this thread and I rely on these fantastic open source apps daily:

1. AntennaPod -- podcast app
2. Orgzly -- Todo lists / reminders / notes via org files. Can be synced via syncthing.
3. Aves -- gallery app
4. KeePassDX -- keepass client
5. Prognoza -- weather app
6. Olauncher -- minimalist launcher

Honourable mention: Harmonic -- hacker News app. Not "essential" by any means but it's quite good.

Edit: added prognoza and olauncher

Authenticator Pro. Two-factor authentication app. Open-source. Supports encrypted backups to the file system or any app that can store files. Supports WearOS - Getting 2FA codes on my Samsung watch is way more convenient than having to get my phone.

These might be popular or we'll known, but I do consider them essential:

Moon+ Reader Pro - Ebook reader

Smart Audiobook - Best audiobook reader I've found

Amaziograph - A drawing app that mirrors you drawing movements elsewhere. It is a really fun and soothing drawing app

Imagepipe, remove the metadata of your photos before sending it to an app

For me it's Block This! ad blocking, and every phone I own gets Smartlauncher. It makes every phone the same.

"Sleep Timer" by CARECON GmbH. Its indispensable for adding a generic sleep timer to any audio or video that does not have such a feature.

Privacy Friendly QR-Code Scanner by the research group SECUSO (Security • Usability • Society) at Institute of Applied Informatics and Formal Description Methods (AIFB) of the Karlsruhe Institute of Technology (KIT). They make a bunch of simple privacy respecting apps.

All it does is display the text of the QR code for you so you can copy investigate it.

AndrOBD for connecting to my car OBD2 Bluetooth adapter. It lets you read any diagnostic codes and let's you reset warning lights.

Aegis for managing 2FA tokens. Weawow for weather. MiXplorer for file management.

Universal copy - turns your screen into a notepad basically where you can copy any text currently showing on it - super handy for a multitude of things

Twilight - you can set a timer or match it with the sunset/sunrise to redshift your screen to help ease the transition to bedtime by negating the blinding blue screen. I have it set to an hour before I'm supposed to be in bed and love it.

If you have a Samsung: Goodlock - shit let's you customize to your heart's content without the need for a different launcher. Pretty awesome imo for a low barrier entry customized phone setup.

Marco Polo - I use this with my family constantly since we live across the world from each other; it's a short video messaging service where you communicate with short videos and history is kept indefinitely. Like snapchat but no disappearing ability and no ads or influencer shit. They also handle it pretty well when you lose a loved one by preseving their account separate from their phone number as, obviously, they won't have ownership of that anymore. Good dev team who listens to feedback and not owned by a bigger corp afaik.

Auxio. It is the best local music player for android I have ever used.

Musicolet is my preferred music player OurGroceries is what I use to keep shared lists with my family (mainly grocery list, but also things like a travel check list and favorite meals for when we can think of what to have for dinner).

White noise generator is great if you use one normally but don't take it on travel.

I like getting relevant, regional emergency alerts. So I use CodeRed. Customize to select which alerts.

JuiceSSH comes in handy sometimes

WifiAnalyzer to check 2.4G in the area for congested channels

KWGT and KLWP. Worth every penny to skin your home screen to your exact desires. It's basically like adding several layers of extra functionality to your launcher with custom coding and some surprisingly great GUI tools. I've seen people do some insane shit. Throw in Tasker and you got a stew going!

I use the Hermit app to "make" mini-apps of websites I frequently visit. They can also be sandboxed too.

I use Qmee to make a bit of money on the side. Made 1100 dollars off the app. It's tedious and low paying but it keeps me in Amazon cash and I don't doom scroll that way. I've managed to buy myself many, many pairs of shoes via survey apps, Qmee is the best one.

YMusic. It lets you listen to only the audio from YouTube videos, even when the screen is off. You can create music playlists, shuffle, and turn the screen off, with almost no ads.

A Strobe Tuner is fantastic if you play music. I've been using the open source one by Adam Foster for years, but heard the A4Labs version is good too.

For me 2 of the most essential are "color blind assistant" and "color blind pal".

Netguard firewall. I wouldn't run Android without it protecting my privacy from connecting to invasive domains.

croc syncthing bitwarden firefox protonmail

Pdanet for usb tethering without it counting as hotspot