if you make some kind of support request here, it always helps to attach the full output of snap version so people trying to help can see what versions of the different parts involved in snap handling are installed on your system.
regarding the DNS error, it seems openra makes some use of avahi, is the avahi-control interface connected ?
techincally snaps should not really differ between a PC install and a RPi install, so special tutorials should not be necessary (famous last words indeed )