At some point NAT66 prefix translation has stopped working on the 1.5 nightly.
Here's a sample config and ip6tables output showing nothing configured based on the config.
```
fahad@vyos-vps:~$ show interfaces
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface IP Address MAC VRF MTU S/L Description
----------- ----------------------------------------- ----------------- ------- ----- ----- ----------------------------------------------------------------------------------
dum0 100.1.2.3/32 da:f4:74:8c:09:7c default 1500 u/u Dummy interface for DNS
eth0 94.250.203.65/23 00:50:56:44:bf:17 default 1500 u/u
2a02:c206:2076:2040:250:56ff:fe44:bf17/64
2a02:c206:2076:2040::1/64
lo 127.0.0.1/8 00:00:00:00:00:00 default 65536 u/u
::1/128
tun100 2001:470:1f12:452::2/64 n/a default 1476 u/u HE.NET IPv6 Tunnel. Routed Prefixes: 2001:470:1f13:452::/64 and 2001:470:ca0e::/48
vti10 10.0.0.2/30 n/a default 1420 u/u
vtun20 100.100.0.1/32 n/a default 1500 u/u
wg01 172.31.10.1/24 n/a default 1420 u/u Roadwarrior Client WG VPN
fd99:d781:643e:8308::1/64
wg10 172.31.250.1/24 n/a default 1420 u/u WG Tunnel to OpenWRT wrt1900acs for ipv6 gateway
2001:470:1f13:452::f:1/64
wg20 192.168.34.1/24 n/a default 1420 u/u WG Tunnel to VyOS-RTR-N1
wg21 192.168.35.1/24 n/a default 1420 u/u WG Tunnel to VyOS-RTR-N2
wg30 2a11:6c7:f01:3fa::2/64 n/a default 1420 u/u
fahad@vyos-vps:~$ show config commands | grep nat66
set nat66 destination rule 9001 description 'Wireguard Incoming NAT66 prefix translation'
set nat66 destination rule 9001 destination address '2a02:c206:2076:2040::a:0/112'
set nat66 destination rule 9001 inbound-interface name 'eth0'
set nat66 destination rule 9001 translation address 'fd99:d781:643e:8308::a:0/112'
set nat66 source rule 9000 description 'Wireguard Outgoing NAT66 prefix translation'
set nat66 source rule 9000 outbound-interface name 'eth0'
set nat66 source rule 9000 source prefix 'fd99:d781:643e:8308::/64'
set nat66 source rule 9000 translation address '2a02:c206:2076:2040::/64'
fahad@vyos-vps:~$ ip6tables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
fahad@vyos-vps:~$ ip6tables -t nat -nvL
Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
```