I see, could be the Nvidia card/drivers. I blocklisted Nvidia almost a decade ago, so my article will have a clear blind angle on that part. I tested the setup only on two machine: my full AMD workstation and on laptop with a Intel GPU.
I'll publish it tomorrow, probably many things I reported on it (for KDE Neon User Edition) should work on other distro, as I also have this time more Flatpak around, and tips related to KDE Plasma latest (but over a 24.04LTS 'old' base).