From IFWiki

F-Droid is an donation-funded app store alternative to Google Play, Amazon App Store, Samsung App Store for Android devices. It distributes FOSS (Free and Open Source Software, Free_Software_IF) applications for the Android platform. Text Fiction, Son of Hunky Punk, L9Droid, Instead (INSTEAD), Quest Player (QSP) are currently available IF apps on F-Droid