[tde-users] *not* TDE related (at least not directly)

Hello mailing list, This is not TDE related, but maybe someone can help. My main machine has stopped working. It boots to a dark screen when loading the system. - I can go to the BIOS - I see the GRUB menu - I see the initial (text) messages, but then the screen turns black - This happens for three OS installed on different disks (MX-21, MX-23, Debian Buster), so it's not a disk problem. - I can boot "Image for Linux" (from USB) and access the partitions (graphical screen, but at low resolution). The computer uses an integrated video card (AMD Ryzen 2400E) I'm trying to find out if this is a motherboard problem or a processor problem. For the moment I am thinking the problem is related to higher resolution, but I can't figure out what causes it. The important data has been migrated to another machine so no worry there, but I simply want to understand. What log am I to look for (all three systems are Debian based)? I'm thankful for any suggestion :) Thierry