Created attachment 1948661 [details]
journalctl  --no-pager |grep kwin_wayland

Description of problem: Visual artifacts and intermittent interface freezes when applying a particular theme with transparency enabled.
  I’ve noticed a transparency option in KDE settings (workspace behaviour - Desktop effects - Translucency), but it only makes windows translucent during dragging. I tried to attempt making everything transparent and see how it goes. After some searches it appears you have to apply a theme that has it in settings. There was one amoung several available called “Spectrum Spite”, which made the taskbar and the rest of the windows transparent. Around then the problems started:
  1) several GUI applications installed into a toolbox, in particular this one:
doublecmd-common.x86_64                     1.0.10-1.fc38              @rawhide 
doublecmd-gtk.x86_64                        1.0.10-1.fc38              @rawhide 
When i ran them no matter inside the toolbox (or outside with toolbox run), their GUI and mouse froze intermittently (for several seconds I can't type, move windows or cursor, or type, then everything goes back to normal for several seconds; repeat). Intermittent total freezes (very annoying!) lasted until the app was running outside the toolbox.
  2) at least one app installed outside the toolbox - VLC flatpak - had visual artefacts - flickering and distorted title bar - while  playing videos. Several others did not (MPV).
When I’ve applied the standard Breeze theme (without transparent effects), all the issues disappeared - even VLC window is without artifacts, and GUI programs that I launch out of the toolbox no longer cause freezes (at least it seems).

Version-Release number of selected component (if applicable):
Fedora-Kinoite-ostree-x86_64-Rawhide-20230306.n.0 with KDE Plasma 5.27.2

How reproducible:
Always

Steps to Reproduce:
1. install Fedora-Kinoite-ostree-x86_64-Rawhide-20230306.n.0 and make an external monitor primary with 150% or 200% fractional scaling (not sure if it's important).
Create a toolbox and dnf install doublecmd-gtk inside the toolbox.
2. install VLC 3.0.18 from Flathub in Discover.
3. in KDE settings (Workspace behaviour - Desktop effects) enable translucency option;
4. in KDE settings (Appearance - Global Theme), select Get New Global Themes
5. select, download and apply “Spectrum Spite”
6. play a video file in VLC placed on an external monitor; the titlebar and window border should flicker; and the title bar possibly be distorted.
7. run doublecmd from inside or outside of toolbox: the GUI will show up and frezees will start until the app will be closed.

Actual results:
1) several applications (like VLC) have their window border and title bar distorted and flickering.
2) several GUI applications, at least in a toolbox, like doublecmd, cause severe systemwide freezes, making the system unusable.

Expected results:
All applications have their GUI without artifacts or flickering.
all GUI applications (including those in toolboxes) run without casing any freezes.

Additional info:
1) Fractional scaling enabled: 150% on one screen and 200% on another.
2) VLC titlebar artefacts were the worst on the usb-c display chained through thunderbolt.
3) several wayland-related errors in the logs (see the attached text file)
4) $ glxinfo | grep OpenGL:
OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) Xe Graphics (TGL GT2)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 23.0.0
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.6 (Compatibility Profile) Mesa 23.0.0
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 23.0.0
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions: