VyOS 1.3 does not support matching an ipv6 peer even though, FRR 7.5.1 (which is bundled with VyOS 1.3) supports it:
Working example accessing FRR directly through vtysh:
route-map test permit 1 match peer fe80::2
Error from VyOS configuration:
# set policy route-map test rule 1 match peer fe80::2 peer must be either an IP or local Value validation failed Set failed
I believe the change is a matter of adding an ipv6-address validator to https://github.com/vyos/vyos-1x/blob/current/interface-definitions/policy.xml.in#L957