Hey!
I'm having the same issue with the same forge version of Minecraft over LAN. Vanilla LAN of the same version works. I, the attempting client, could host a modded LAN of the version, and the usually attempting host was able to join; but they could not see it as an ooen LAN server in their connections. Using my internal IP in a direct connection with the right port still let them connect to the lan server though. The same results couldn't be produced the other way around.
Firewall and network connection settings have been evaluated, we can't figure out what to do