German - this looks like it's intended behavior, the help message in the openstack client actually says the default is TCP:

  --protocol <protocol>
                           IP protocol (ah, dccp, egp, esp, gre, icmp, igmp,
                           ipv6- encap, ipv6-frag, ipv6-icmp, ipv6-nonxt,
                           ipv6- opts, ipv6-route, ospf, pgm, rsvp, sctp, tcp,
                           udp, udplite, vrrp and integer representations
                           [0-255] ; default: tcp)

But I'm not sure I agree that was a good choice, especially given it was not discussed, and not even in the commit message of the change that did it.

I'll propose a change for it and see what happens.