Information is incorrect under the header “Migrating from Relay → For the joining player”.
https://docs.unity.com/ugs/en-us/manual/mps-sdk/manual/migration-path#Migrating_from_Relay
Codeblock has a mistake in the method BuildClientRelayServerData
hostConnectionData: joinAllocation.ConnectionData,
should be:
hostConnectionData: joinAllocation.HostConnectionData,
otherwise can’t Relay connect to a host on the same machine when testing Relay. Wasted a whole effing day smh.