Hi Paul, 
thanks a lot for your replies. 
I´m sorry, I don´t quite understand.
Do you mean I should see if the live version (install media) of Linux Lite works with the laptop?
On the site the link to which you provided they suggest adding “nosgx” as a kernel boot parameter.
I forgot to mention that I tried that as well. But it didn´t help at all - unless I misspelled it. That´s always a possibility.
What I don´t quite get is: why would a system update change BIOS (or rather UEFI) settings 
… and doing it in a way that no changes can be perceived visually. 
Many greetings from Rosika 