Any workaround will keep breaking because this is the incorrect layer to solve the problem. It is not on systemd or zerotier.. it is sshd that needs to allow setting the IP_FREEBIND socket option to allow it to listen on addresses that are "not yet" or "ever" configured. }
here is the patch to do it https://bugzilla.mindrot.org/attachment.cgi?id=2763 , it is correct but unfortunately openSSH developers did not accept it.