Wayland is just a set of protocols, which work fine (albeit with limitations) when implemented properly. So if KDE’s implementation of its share of the APIs works correctly with Intel and AMD GPUs, but not with Nvidia ones, the culprit is extremely likely to be the latter.
KDE Plasma 6.0 Approved For Fedora 40 - Including Dropping The X11 Session (www.phoronix.com)