Thanks for you post EricJH!
a black box will show up
So yeah, the problem persists.
I found the ports at the ubisoft website and added the rules with my mac address as target, like you said.
But nothing changed. I even changed the application rule to log every communication but basically there is only a "check running gameservers in lan" request that pops up in the log.
I don't know what I can do now.
Any other thing I can try?