Thunderbird for Android – Open Source Email App for Android (fka K-9 Mail)

AnkiDroid: Anki flashcards on Android. Your secret trick to achieve superhuman information retention.

Android application to analyze WiFi signals.

DAVx⁵ is an open-source CalDAV/CardDAV suite and sync app for Android. You can also access your online files (WebDAV) with it.

A privacy-conscious Android keyboard made for your thumbs

Enhanced fork of FreeOTP-Android providing a feature-rich 2FA authenticator

Twitter and Mastodon client for Android

A different kind of blue filter android app, enabling the built in black and white mode in android without the use of an overlay screen