Update of Leap 15.6 has broken gui

I would switch to the Nvidia-kmp from Nvidia Repo:

zypper dup --allow-vendor-change --auto-agree-with-licenses --from https://download.nvidia.com/opensuse/leap/15.6

Because highest Version of the open-kmp is:

nvidia-open-driver-G06-signed-kmp-default        | Paket      | 570.172.08_k6.4.0_150600.21-150600.3.56.2

but in the Repo is also the highest Version:

i+ | nvidia-driver-G06-kmp-default | Paket | 580.82.07_k6.4.0_150600.21-lp156.39.1

After this, before you restart, post:
zypper se -si nvidia