Debian for me on all VMs and all servers that do not run a hypervisor. Can’t stand the snaps that Ubuntu introduced in a very aggressive and intrusive way. Don’t need a GUI either so Debian is a natural choice for me. Pro tip for non critical services: Enable the backports repository to get modern packages with recent versions. I’ve never encountered a problem, but still would not recommend it for a mission critical service.
Memtest86 didn’t find any problems, but I’ll try out some different RAM configurations. Got some spare DIMMs flying around…