Electron app won't close in i3

I still use the old - and last - official Linux .deb package for Teams and sure enough, it doesn't behave properly in i3: Teams starts and shows up in the systray but the window is fullscreen and won't close. I have to keep a workspace around just for Teams.

I suspect Electron of course. Electron doesn't integrate well with any Linux desktop environment. Just wondering if someone knows if there's a trick to make it close in i3.