Joining local multiplayer stopped working after recent patches

We used to play together and it worked without issues. But after the recent patches (1.20.2+), I can't join anymore. The multiplayer game is not visible in the list. I can't even join directly by IP, although ping works. It's not a network problem, other network related things work, computers can see each other.

I downgraded to 1.20.1 and it works again, so there must be a bug somewhere.

One computer is running Windows 11, the other is on Windows 10. 

Both using minecraft-bundled java.