+1 to Obtainium; open source need not the app store.

broadmode

satoshiplanet

I've been using Obtainium for a few months now and there are things I like about it but is far from ready for most people. 

In my use you have to update apps one at a time. Often you have to select which APK to use. It requires more attention. 

Unless you want that level of control I don't think it is a big of a win over Fdroid. 

Eobard

Would also recommend to use `Obtainium` to allow you to download open-source apps from any code repo - https://github.com/ImranR98/Obtainium

No need for FDroid most of the time. Allows you to control app updates too.