I hesitated with the update and waited till today, because I have hybrid graphics with optimus-manager.
I did the update today, then recompiled optimus-manager-git, rebooted and everything seems to be OK.
It’s possible I will find some breakages later, but so far, the system boots correctly, everything loads, Steam works, I can switch between GPU modes, Steam is showing correct drivers (intel, noveau or Nvidia - depending on the GPU mode).
So far so good.
I had some info about the lack of the folder:
grep: /etc/X11/mhwd.d/nvidia.conf: No such file or directory
but that’s expected on a proper optimus-manager install. This didn’t create any problems so seems like it worked well anyway.