Check out the Discord for The Coalition of the Horde community. It’s a Moon Guard community discord for Horde players specifically. I am sure you can connect with a lot of your fellow BE RPers there and find a guild or two as well.
I also second The Phoenix Legion if you’re looking for Belf RP. Every interaction I’ve had with TPL has been great - they are a pretty active group as well and everyone is awesome.
I would also recommend checking out The Horde Vanguard which is a Horde-focused community made of multiple guilds and individuals. We actually just finished a 2 day mini campaign defending Thunder Bluff and it was amazing. I cant put links on posts but THV has a server post up with a link to the server.