Recommended open-source Android apps

Apps I'm currently using and recommend to everyone.

Following my switch to microG (an open source re-implementation of Google Play), some Google Apps stopped working (read here). During my search for replacements, I discover many open source alternatives. These are the apps I’m currently using and recommend to everyone.

Aside from the below list, check out the NanoDroid’s list of other great open source alternatives.

F-Droid / Aurora Droid + Aurora StorePlay StoreF-Droid is an app store for open source apps; Aurora Droid is an alternative F-Droid client with more features, like the inclusion of many popular third-party repo. Aurora Store is to browse and install apps listed in Google Play without a Google account, while still offering support for Google account login to download purchased apps. Install Aurora Services as a privileged app to enable auto-installation.
Fennec F-DroidFirefoxIt’s an official build by Mozilla for F-Droid with less proprietary components (Google Services Framework?). Particularly suitable for microG.
BromiteChromeChrome sans Google proprietary components. Installable via F-Droid/Aurora Droid by importing the repo.
Simple Calendar + DAVx⁵Google CalendarGoogle Calendar doesn’t work with microG. It’s part of Simple Mobile Tools, so it’s open source and include dark theme. Use DAVx⁵ to sync calendar and contact. Google uses proprietary protocols instead of CalDAV and CardDAV, so data migration is required.
Simple GalleryGoogle PhotosThe only reason I use Google Photos is the ability to view panoramas, despite having no issue with microG. Since Simple Gallery is part of Simple Mobile Tools and supports panoramas, I gladly switched.
NotepadGoogle KeepGet the job done without fuss. No note syncing, but I don’t need it.
KeePass DX / Keepass2AndroidKeePassDroidKeePass DX utilises Material theme so it looks more modern and feels lighter. Currently, it does not support database with attachment well (see #115 #183); alternative is the Keepass2Android. There is an online version which supports opening database from the cloud backup.
LibreraFBReaderMost advanced e-book reader. Highly customisable. Supports ePUB, PDF and Kindle.
Pdf Viewer Plus, PDF Viewer, LibreraGoogle PDF ViewerFor a simple pdf viewer, I liked Google PDF Viewer due to its minimal size (5MB). An open-source alternative is Pdf Viewer Plus. It uses vertical scrolling just like the Google’s (and most desktop PDF viewers). Librera offers much options, but it’s twice as big; I like the ability to switch text background colour, between day and night mode. For bare minimal app, PDF Viewer does it job with just 1.4MB.
Unit Converter UltimateThe only unit converter app that you would ever need. Supports every practically possible units including currency.
Aegis / andOTPGoogle AuthenticatorOpen source and dark theme.
Catima, Loyalty Card KeychainGoogle PaySimply to store loyalty cards with barcode.
Organic Maps, OsmAnd, HERE WeGoGoogle MapsOsmAnd and MAPS.ME are open source and utilise OpenStreetMap. They do not have public transport info though. Use Transportr for that. Organic Maps is a fork of MAPS.ME without the proprietary bits and it’s available on F-Droid.