This makes no sense to me, but maybe to you?

So I have a EOS Plasma system working fine. Mostly doing KVM/QEMU VMs. Then I got the itch to install my old Steam game Portal/Portal2 which requires Steam. I got it installed per the wiki and played it awhile then today I spun up a new VM and tried to installed Linux Mint Debian Edition 5. The install kept failing about 50% in and exiting back to a reboot where it failed at grub. I tried several times and finally it locked my workstation up completely. I had to power it off by pulling the cord.

I check the ISOs sha256sum and it was good. So the only thing I could think of was the install of Steam. So I restored to a btrfs snapshot from before I installed Steam and now everything is working great. I got the LMDE5 VM working as well.

Does it make sense that Steam could cause KVM/QEMU to fail mysteriously even when it was not even running in background??

What VM technology are you using.

Steam itself? Probably not. However, did you do any updates since that snapshot or did steam install any dependencies?

What is your GPU?

I using libvirt kvm qemu for VMs.

Intel Iris Graphics are built-in. Steam require some 32 bit stuff and a lot of libraries. There were some updates but after I restored to the pre steam point, I ran yay to update the system. So the only thing that to me is suspect is Steam. I don’t need it but it was a good test of btrfs snapshots and btrfs-assistant.