Using iproute2, you can use “ip addr add XXXXX peer YYYY dev ZZZ” to specify the address of the remote endpoint, for example using an ULA :
peer ADDRESS the address of the remote endpoint for pointopoint interfaces. Again, the ADDRESS may be followed by a slash and a decimal number, encoding the network prefix length. If a peer address is specified, the local address cannot have a prefix length. The network prefix is associated with the peer rather than with the local address.
Is there a way to do the same thing using VyOS configuration options?