Comment # 13 on bug 1201995 from Joachim Banzhaf

not sure where the x sessins startup log is (not /var/log/Xorg.*.log and not
~/.local/share/xorg/Xorg.*.log) 

Anyways. I switched UEFI setting from switchable grafics to the only other
setting. I guess it meant intel only because I don't see the nvidia stuff
anywhere now.

Didn't help :(

with nomodeset: okish graphic (just slow, no brightnes control, ...) 
without nomodset: black screen as described.

So, if you plan to buy an IdeaPad 5 Pro 14ITL6 for linux, I really cannot
recommend that right now...