Extreme Plasma UI delay in Wayland session


I installed Kubuntu on a friend’s desktop, and they need Wayland because they use two displays at different scales. Unfortunately, Plasma on Wayland is extremely slow compared to X11. After login the desktop takes something like 15 seconds to load (less than 5 on X11), and when Plasma is called on to do something by a mouse input (make menu appear, select menu item, etc.) it similarly takes a really long time (5-10 seconds) for the result to materialize visually. There was no delay when it came to moving windows by dragging with the mouse.

They have an nvidia card (GTX 1060) and are using the proprietary nvidia drivers, which I suspect might be relevant.

I’ve tried to look for similar issues but haven’t found any exact matches. I was just wondering if someone might have some insight.

I remember a few versions ago copying any images to the clipboard would cause Plasma on Wayland to be less responsive. Try cleaning the clipboard history in the applet and see if it helps. I’m pretty sure that has been fixed in Plasma 5.27, so try installing a new version of Kubuntu (non-LTS) or try KDE Neon User Edition.

If that’s not the issue then I’d recommend sticking to X11 for the time being.

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Thanks for the tip. The problem occurs on a fresh boot so I believe the clipboard should be empty, but I can try that next time I have access to the machine.

And I assumed all along that Kubuntu shipped 5.27 but it looks like that isn’t the case! Thanks for pointing that out. I think it explains a few things. I might just install the non-LTS Kubuntu and see what that does.

Thanks again!

Did you find a solution? I am having the same issue on Ubuntu 22.04 with the 535 and 545 Nvidia driver

Might be your problem right there, try removing one of the drivers (I would purge it completely and reinstall the correct drivers)
Another user that seems to have had a similar issue here:

Just make sure you use the latest available drivers FOR YOUR DISTRIBUTION.

General instructions here: https://ubuntu.com/server/docs/nvidia-drivers-installation