at the time of writing this (September 18 2024) I got everything needed to make the game work (Framework 1.20.1, Controllable 1.20.1), but I can't play on any Realms for some reason.

It says "Client Incompatible! Your client is not compatible with Realms. Please use the most recent version of Minecraft."

I can only assume it is because the latest version of Controllable is 1.20.1, whereas Framework and Forge itself both are updated to 1.21.1, which is the latest version for Minecraft vanilla. if I am mistaken and you can play on a Realm with the latest version of Controllable, please let me know ASAP!

It's a bug, seem the issue came from Framework or Controllable that request server side and not client side only. Crayfish needs to fix this has possible. I got same issue when i host my game with Essentials and it's make my friend unable to join without one of these.