Ghost apps in installed apps list appeared - needed to clear app data to make them vanish

• Device OS and version: Android 8.1.0
• Device model/manufacturer: Aquaris X
• F-Droid version (in the About screen): 1.3.1
• F-Droid privileged extension version (if installed): --

What did you do? (clear steps if possible)

• Installed some apps with F-Droid 1.2.2 some time ago
• Let some time go by
• OS got upgraded from Android 7.1 to 8.1
• F-Droid got upgraded from 1.2.2 to 1.3.1
• Looked at the installed apps list

What did you expect to see?

• All installed apps with nice icons

What did you see instead?

• Many more than the installed apps
• Some with icons, some with standard greyed icons
• Many listed apps without an install/de-install button
• These apps may have been installed once (not sure)
• Some of these listed apps I probably never installed

Do you find a workaround?

• OS App settings: clear app cache didn't work
• OS App settings: clear app data made the installed app list rebuild itself and everything appears to be okay

I still think it might be some non-desired behavior.