Pi-hole itself is able to list all DHCP servers on the link(s) it is connected to
pihole-FTL dhcp-discover
I'd guess it may also be the most reliable tool to do so yet - see also the discussion in Reliably detect all DHCP servers on a network? that lead to Pi-hole supporting it.
However, since you would run that command from within some kind of container or virtualised environment, it would depend on that environment's network configuration whether pihole-FTL would see just the virtual network or your actual network link. It would only work for the latter.