Plasmabar not auto-hiding

[RedEtherbloom]

The plasmabar never hides due to inactivity, in turn constantly blocking part of my small screen.

The visibility is set to auto-hide, a fresh KDE installation didn't fix it either.

System is Arch Linux, KDE version is 5.27.9, i3 version is 4.23.
i3+KDE is setup according to Option 2: New XSession.

Is plasmabars auto-hide functionality actually dependent on some feature of KWin?
I iirc could not find any DBus Message instructing plasmabar to hide, in a pure KDE setup.

Any ideas of how I could manually trigger the hide functionality?
I couldn't find plasmabars source code, so I've run out of ideas what else I could try.