... and good alternatives, where available. To the best of my knowledge, and no guarantees obviously. All the apps listed here are distributed with libre licences (except where otherwise stated), but some may rely on non-libre backends.

Productivity

• DAVx5 - the easiest way to synchronize your Nextcloud contacts/calendar/tasks with corresponding Android apps. GPLv3. Available on F-Droid.
• K-9 Mail, or these days it is perhaps just as well to use Thunderbird for Android.
• Nextcloud
• Nextcloud Notes
• Tasks.org - a great tasks app that synchronizes with your Nextcloud tasks.

Chat, messaging

• Signal messenger. The app is FOSS, but relies on a proprietary and centralized service.
• Nextcloud Talk
• Beeper

Keyboard

• Unexpected Keyboard, F-Droid - keyboard with a smart swipe-inside-each-key UX that exposes a massive amount of special characters in a smart way.
• HeliBoard, F-Droid
• https://github.com/futo-org/android-keyboard
• Thumb-Key - cool keyboard meant for thumb typing and swiping inside each key.

Audio & video

• Audio Recorder, F-Droid. Easy to integrate with Nextcloud's "Auto Uploads" functionality, in my experience. But the default quality settings (bitrate, etc.) are quite low and I suggest raising them.
• Jellyfin, F-Droid - mobile client for Jellyfin media server.
• NewPipe, F-Droid - I recommend you install it on F-Droid using their repo to get updates faster (but note that this means you trust their repo to push updates to your phone).
• Tempo - music client for Subsonic-compatible servers.
• VLC

Misc

• Binary Eye, F-Droid - a competent QR code scanner.
• FreeOTP+, F-Droid - 2FA authenticator.
• Kvaesitso launcher - it looks great by default and can be customized in lots of useful ways.
• Librera Reader, F-Droid.
• OpenKeychain - in combination with Password Store to sync pass to Android.
• OsmAnd - OpenStreetmap for Android.
• Tailscale - app is FOSS, but the underlying service is proprietary, but can replaced with Headscale (but unfortunately I cannot recommend it - tried it once and never figured it out).
• Transdroid - Bittorrent client that lets your monitor and control your server.
• Transportr - public transport timetables. Works well in Stockholm.
• Tusky - Mastodon client that works well with multiple accounts across different instances.
• Wallabag

The issue is when you don’t have an account, it’s quite difficult… For someone who doesn’t know where to look for. Let’s see how we can bypass their “Join LinkedIn or Sign in” message.
First, you need to find the profile of the user targeted. Any search engine should do the trick. Usually, it’s something like :

https://www.linkedin.com/in/username

Copy that URI, and paste it to … wait for it … A Google website. The address is : http://search.google.com/test/mobile-friendly. It’s a page to test if your website is mobile friendly 😂.
Hit the test button, wait a bit, and then click on View tested page.
Copy all the HTML, and paste it to https://codebeautify.org/htmlviewer, and hit the RUN button. Now, you should be able to see more information on that profile.
Of course, if you prefer you can copy/paste the HTML code in a text file. Rename it with the .html extension before opening it with your browser.

Reproduced most of the original note above just in case of linkrot.

Very cool :-)

Here's my modest profile, for example.

Via https://discuss.systems/@ricci/113684446286253550

Explore our hand-picked collection of out-of-copyright works, free for all to browse, download, and reuse. This is a living database with new images added every week.

Via https://mastodon.social/@publicdomainrev/113794180924217390

• Mobilizon - developed by the well-known Framasoft. With a web forum and a Matrix chat, awesome choices.

Mobilizon instances

• https://stockholm-events.nu via https://mastodon.social/@zeank/114110668049687721
• https://organisera.org via https://konstellationen.org/2025/01/24/organisera-mobilizon

kv4p HT is a homebrew VHF radio that makes your phone capable of voice and text communication completely off-grid [...] radio simply plugs into the USB C port on your Android smartphone and transforms it into a fully-fledged handheld radio transceiver.

Looks really cool. But then of course I know nothing about ham radio.

From Better Posters I learned about the idea and that there is a serious effort to create such a registry: ConfIDent.

But is it ready for prime-time?

• Terms of use only available in German, as far as I can tell.
• Account creation flow involves manually requesting an account, but it is not clear to me who is behind this service. Strike that, the Imprint makes it clear: the Ministry for Science and Culture of Lower Saxony, Germany.