The Racknerd $35/yr seems to be the 500MB RAM VPS with a 500GB/mo network data limit. That’s probably sufficient power for a wireguard endpoint for ingress, but that’s pretty low network data limit if you’re putting a media server behind it (10GB/hr of video isn’t unexpected, data is counted twice when having to ingress+egress thru the endpoint=25 hours of quality video per month)
I think you found it was exactly what I said? You worked around it by changing a specific setting directly in Firefox that disables the exact check I mentioned without needing to disable all of private DNS in Firefox though.