We have exactly the same issue. Qemu 6.1 is totally broken or incompatible with libvirt /
vdsm.
The qemu process is launched properly (no libvirt / vdsm error, and no error in the qemu
log file) but it doesn't boot at all, no spice, no network, nothing.
Downgrading to 5.2.0 (from 6.1.0) has fixed the problem for us.