OK, does Leap 15.4 kernel show the similar warning/error related with nouveau? Please attach the dmesg output. You can try the kernel from OBS Kernel:stable:Backport repo, too. This is a kernel that is equivalent with TW, the latest upstream 5.18.x stable kernel. If the same problem is seen with this, you should report it to the nouveau upstream, preferably via gitlab.freedesktop.org Issues.