Gab App Store - Gab App Store is the place to find apps either made by Gab or Mastodon clients that work with Gab.
Fnd - Browse Apple App Store and iTunes on the Web
Apple App Store - Install apps on your iDevice via the App Store.
JazzMyApp - Let JazzMyApp surprise you with amazing apps everyday. Try it out yourself.
F-Droid - F-Droid is an interesting alternative for Android users who want to try something different and not have to use the Goole Play store all the time.
Cydia - An alternative app store for jailbroken devices.