Problem with full-screen applications and fractional scaling for HiDPI monitors

This is another problem I experience with fractional scaling/HiDPI and Ubuntu 20.10.

I have a setup with 2 normal DPI monitors and one HiDPI with 150% zoom.
The problem is when an application requests full screen (i.e. firefox and a video in youtube, VLC, or even a wine game). Then the application changes (properly) to full screen, there’s a flicker, the resolution changes, the screen flickers again, another resolution change and the monitors are left in a total mess.

With firefox/youtube things are even worse. The screen goes into infinite loop of changing resolutions.

If I disable fractional scaling and put everything into 100% or 200%, no problem appears. Even if I keep on fractional scaling, but put either 100% or 200%, still not problem appears. Same, if I use fullscreen on a monitor with no fractional scaling. But, when I try to put full screen for a fractional scaling monitor, chaos emerges.

I am really confused on how to approach this problem… any ideas?

EDIT I am using X11 backend, not wayland and Ubuntu’s Gnome as Window manager.

EDIT 2 When I change from default Gnome to Budgie, there I can launch fullscreen apps correctly. So it looks like a Gnome issue. Any hint how to solve it or where should I report it?