Looks like I had to poke some more holes in my outbound firewall rules to support Minecraft v1.12.1 on the XBox live connection for Realm play.
UDP 32411, UDP 32600, and UDP 32826 were being blocked outbound. It seems v1.12.1 prefers 32826 a lot but will bounce between 32826-32999.
My full outbound Minecraft rule consists of:
TCP/UDP ALLOW OUT 19132,19133,19135,25565,26000-28000,32400-32499,32600-32999