I reckon, i was able to identify the root cause of my problems being me.
This Kernel upgrade failed again on my PC with not being able to launch the new leap version due to SHIM issues. So i rolled back the Snapshot and ‘upgraded’ from the original Leap 15.5 USB.
Bur this time the boot menu did NOT fix itself - instead the default still goes to the new Kernel and fails on GRUB2 due to SHIM, telling me, that i should load the Kernel first.
Question 1: How can i remove a not wanted Kernel from my System? (In this case the failed 6.7 Kernel)
Since this failed to me similar as me having had tried to upgrade to Tumbleweed before, i guess that Suse is smarter than me with Linux and i must have made a common mistake in both scenarios.
I gut feeling is that the ‘MOK Management’ blue screen having appeared after the upgrades would be important. In both cases i went just for ‘Continue’ without selection of any key because i am not aware having defined a key in UEFI nor did i get any offered in the MOK’s menu for keys.
But then i found this good documentation, which explains that there should always be a key after an upgrade. And this chat in our Forum suggests, that there needs to be done something.
Sadly i am not (yet) smart enough to understand, what i am supposed to do, when the blue ‘MOK Management’ window appears.
Question 2: Does anybody have a hint, tip or link to a good read of what i am supposed to do with that MOK Management would be very much appreciated.