ip6tables-translate -t nat -A postrouting -o eth0 -p tcp -j SNAT --to [fec0::1234]:80
nft 'add rule ip6 nat postrouting oifname "eth0" meta l4proto tcp counter snat to [fec0::1234]:80'

ip6tables-translate -t nat -A postrouting -o eth0 -p tcp -j SNAT --to [fec0::1234]:1-20
nft 'add rule ip6 nat postrouting oifname "eth0" meta l4proto tcp counter snat to [fec0::1234]:1-20'

ip6tables-translate -t nat -A postrouting -o eth0 -p tcp -j SNAT --to [fec0::1234]:123 --random
nft 'add rule ip6 nat postrouting oifname "eth0" meta l4proto tcp counter snat to [fec0::1234]:123 random'

ip6tables-translate -t nat -A postrouting -o eth0 -p tcp -j SNAT --to [fec0::1234]:123 --random-fully --persistent
nft 'add rule ip6 nat postrouting oifname "eth0" meta l4proto tcp counter snat to [fec0::1234]:123 fully-random,persistent'