Comment # 6 on bug 1201995 from Joachim Banzhaf

(In reply to Stefan Dirsch from comment #3)
> would recommend to use 
> 
>   prime-select nvdiia

copy from forum on what I tried already.

* nomodeset in the kernel commandline with prime-select intel (no nvidia or
nouveau) is the only way to get a stable display

* nomodeset and nvidia -> no X, just frozen vt console (same with startx as
normal user and as root. Killing X gives back console)
* without nomodeset X always starts, but with the black screen flicker problem
* without nomodeset it does not matter if I use nouveau.modeset=0,
nvidia-drm.modeset=0 (or =1).
* without nomodeset it also does not matter if I use prime-select nvidia or
prime-select intel
* checked the modules are loaded as expected for the different tests. There are
no secureboot problems. Mok key for nvidia is valid.
* no nvidia error messages in dmesg
* no nvidia error messages in .local/share/xorg/Xorg.*.log
* with nomodeset and intel (the "working" config), brightnes control is off

TLDR: 
* I can use the notebook with "crippled" nomodeset/intel
* Open for any suggestion (proprietary or not) to make it better than that.
* Willing to support finding the underlying problem - if not known already