Algorithm doesn't push unused Apps to the inactive section on FP2 LineageOS

[jurigagarinii]

As the title says: none of my unused Apps has been pushed to the inactive section, although I installed the launcher at 2.1.0 and upgraded to 2.2.0, so it has been in use for some time.
I am in a FP2 with LineageOS 14.1

[Roboe]

Hi, @jurigagarinii! Thank you for taking the time to sign up in GitHub to open the issue here.

I guess we haven't notice this missfunction before because in the development process we reinstall and clear multiple times the app, so time-dependant features are elusive. Fortunately I have a secondary device (LOS 15.1, Android 8.1) with the F-Droid builds installed on it and I can reproduce the bug.

I think this could be caused by some system APIs not being available to third-party apps. @jannispinter wanted to workaround a limitation alike using the UsageStatsManager API.