Not sure what you want or need to achieve, but if you use Vulnhub VMs as HVMs on Qubes and these machines expect to receive their ip settings and stuff from uplink, you might want to install a dhcp server on the direct uplink machine (in my case sys-bridge). My suggested readings on that topic:
https://wiki.archlinux.org/title/Dnsmasq
https://wiki.archlinux.org/title/Dhcpd
Don’t forget to disarm your iptables.