[SOLVED] After Update to 26.04 Siganl app display is flickering

[linufix]

Hello everybody,
this is my system:

Betriebssystem: Kubuntu 26.04 LTS
KDE-Plasma-Version: 6.6.6
KDE-Frameworks-Version: 6.24.0
Qt-Version: 6.10.2
Kernel-Version: 7.0.0-38-generic (64-bit)
Grafik-Plattform: Wayland
Prozessoren: 12 × AMD Ryzen 5 3600 6-Core Processor
Arbeitsspeicher: 32 GiB (31,3 GiB nutzbar)
Grafikprozessor: AMD CAICOS
Hersteller: Micro-Star International Co., Ltd
Produktname: MS-7B86
Systemversion: 4.0

After updating to 26.04 LTS version, my Signal apps display is very unstable and flickering.
Hovering the mouse over the Signals window seems to influence the flickering behavior.
When scrolling or viewing pictures the display is heavily disturbed.

Is this a known behavior? And if yes is there something to do about it?

Cheers
Erich

[die.boer]

this looks more like a Signal/Electron + Wayland rendering problem than a general AMD driver problem.

Signal Desktop has had several Wayland-related rendering problems reported upstream. Parts of the interface may not refresh correctly, especially when scrolling or displaying pictures.

As a first test, log out and select Plasma (X11) at the login screen.
If X11 not installed ,then

sudo apt install plasma-session-x11

Then start Signal again and check whether the flickering is still present.

If Signal works normally under X11, that would point more toward the Wayland/Electron rendering path and less toward the GPU itself.

It would also be useful to check whether Signal was installed from the distribution/Signal .deb package or as a Flatpak. The Wayland behaviour can be different between those versions.

I would not start changing kernel parameters, KWin DRM settings, or graphics drivers yet. Those changes are more invasive, and first it should be established whether Signal works correctly under X11.

If X11 fixes the problem, using X11 as a workaround for Signal is probably the simplest option for now, until there is an update to Signal, Electron, or KWin.

Also , do you use fractional scaling?

[linufix]

Hello die.boer,
wow, what a profound answer.
I installed the plasma-session-x11 package, and switched to X11.
Signal works like a charm.
Thank you very much for that hint.
Also checked my signal installation. It is from the repository version 8.28.0 production.
I will stay with this workaround, and check from time to time on updates that might come.
Do I use fractional scaling? I had to look up what this even is. ;-)
But now I can tell, NO, I don't use fractional scaling.
Cheers
Erich

[Kaoruko]

Thank you, I've had a very similar problem regarding games and moving my cursor between monitors, and swapping to x11 fixed it for all of them. There's clearly some bug with wayland when it comes to applications using a hardware cursors and graphics issues.