Is K9 Mail even getting anymore updates on F-Droid at all? Because Google Play is showing an update for it even though I installed K9 mail through F-Droid.
I see that this an issue with certain apps and I don’t see an option to stop it from installing from Google Play. Please help.
Turn off auto updates for those apps on playstore. Enter the app page on storeapp and click on 3 drop down menu at the top right corner. Uncheck auto update for it.
As for F-Droid receiving updates, I updated K-9 yesterday itself from F-Droid. Please sync your repos and check on the app page in F-Droid app.
Yes, almost weekly, buut… do read One new, one broken, one beta, more updates | F-Droid - Free and Open Source Android App Repository
Basically the developer pushes stable versions when they want. If you want to use the latest betas go to the upper right menu, toggle Betas 
Yes, press “Submit feedback” and tell them “Play is buggy, it erroneously tries to update apps with the wrong signature”
known issue Google Play Store tries to update my F-Droid apps :-( 