If you’re not comfortable/familiar with your OS’s networking configuration systems (and I can say I am not familiar at all with how RPI configures networking), then you could also try routed NIC type. This requires using a manual static IP on the parent network (no DHCP) and manual configuration of DNS settings inside the instance. However it also achieves the result of getting an IP from the external network directly routed into the instance. This time without messing with the external network and still allow host<->instance communication.
See How to get LXD containers get IP from the LAN with routed network