incorrect description on firewall group ipv6-network-group ,it should be Firewall ipv6-network-group
vyos@test-firewall# set firewall group Possible completions: +> address-group Firewall address-group +> ipv6-address-group Firewall ipv6-address-group +> ipv6-network-group Network-group member +> network-group
it was tested on VyOS 1.4-rolling-202201120317