Hi @Friedrich1, I hesitate to dare to say it’s done. I experienced too many funny things, but situation is that I spent again some hours trying to figure out some useful Grub parameters. To make the long story short: Useless. Then I started to investigate the BIOS default settings one by one (this one has lot of options/not like Acer). After changing this from “all legacy” to “all UEFI” all started to work fine. Installation and booting system repeatedly.
Frankly speakin, I never looked at this “option rom” page. All I verified beforehand was Securuty (secure boot off), Boot, Options like that…
I first hesitated to set this as fixed, maybe I shoud have waited another day for that. BUT it looks great!!!
Now the work starts to put the data back tweak the system to the scheme I’m used to, as well as I hesitate here…
It was a great motivation @Friedrich1 as w/o your statement that it shoud run, I would not spent so much effort to find out whats wrong. Thank you!
Thanks as well to @megavolt and @stephane for ideas and guidance digging the problems