One thing about #proxmox: it is' mostly just debian with an adapted kernel and services. You can very easily turn your desktop machine into a proxmox server in minutes: https://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_13_Trixie In addition to dedicated machines my desktop mini PC is also a Proxmox Host and a Proxmox Backup server (that is one different kernel and two sets of services and dedicated VM + backup USB disks, the rest is a very normal debian (niri) desktop). The best way is to get a dedicated external disks for your VMS (it creates its own structure so better not mix up your stuff for the VM  disks!). Also you can format your VMs disk as ZFS or LVM-THIN to make things faster / resilient. But to learn you can just setup a disk with .qcows2 files for your disk images, not as good (no per-block  backups) and the like but you get simplicity while trying out.