I’m not much hoepful, but… just in case :)
I would like to be able to start a second session in a window of my current one (I mean a second session where I log in as a different user, similar to what happens with the various ctrl+alt+Fx, but starting a graphical session rather than a console one).
Do you know of some software that lets me do it?
Can I somehow run a KVM using my host disk as a the disk for the guest VM (and without breaking stuff)?
i do not think it is possible, but perhaps the closest thing u can get is virtualbox or qemu/kvm/virtmanager with shared folders, i believe that allows you to passthrough files between guest and host. (shared folders allow you to copy paste something on ur host into them and have them appear in the guest, but dont think i used them before, at least not extensively, so you might have to look into them to check if this advice helps you)
Several solutions have already been posted in here, please do not try to act authoritative when you don’t know the answer. We already saw you asked what VNC is.
The irony is insane. “Act authoritative” even tho I literally didn’t claim to know anything for certain (I do not -think-, perhaps, I believe). Also as other gentleman pointed out, no other comment was there when I tried to help. I asked about vnc -after- I made my initial comment, because a few minutes after other people started pitching in with more accurate and relevant information. I feared the post would go on to have no responses so I tried to pitch in; you don’t have to know everything about everything in order to try and help someone out, all I did was provide my take on the matter, which is better than ignoring the question, regardless of how fruitful or fruitless what I had to say was. People like you are why noobs are afraid if dipping their toes in more technical areas such as linux, and get scared off by smartass supremacists that like to spoil things for no good reason. Sincere, seek help. 🤦🏻♂️