It looks like `show ipv6 route` is broken on VyOS 1.4 rolling:
```trae@cr01b-vyos:~$ show ipv6 route
Incomplete command: show ipv6 route
trae@cr01b-vyos:~$ show ipv6 route
Possible completions:
<h:h:h:h:h:h:h:h>
Show IPv6 routes of given address or prefix
<h:h:h:h:h:h:h:h/x>
bgp Show IPv6 BGP routes
cache Show kernel IPv6 route cache
connected Show IPv6 connected routes
forward Show kernel IPv6 route table
isis Show IPv6 IS-IS routes
kernel Show IPv6 Kernel routes
ospfv3 Show IPv6 OSPF routes
ripng Show IPv6 RIPNG routes
static Show IPv6 static routes
summary Show IPv6 routes summary
table Show IPv6 routes in policy tables
vrf Show IPv6 routes in VRFs
```