Documenting a persistent and time consuming problem I had with Qubes 4.0.1-rc1 on my 15v4. After installing, updating, and restarting, I get this error message:
libxenlight failed to create new domain ‘sys-net’
If you get this message, turn off autostart for all VMs attached to PCI devices. This includes any VMs that will autostart networking VMs (like sys-whonix). My guess is that PCI devices are still being initialized during boot, when Qubes attempts to start the VMs to connect to them. Not sure if this is on Purism or Qubes end.
I wrote a little script to turn on my networking VMs at startup, and found I needed a minimum 5 second delay to prevent this error.