IPSEC Between non-RFC1918 Networks

Trying to figure out how to setup IPSEC for going between networks on Mikrotik routers, not using a tunnel.

I am not trying to LAN-LAN connect sites.. Trying to do this with public IP addresses. IPv6 specifically..

I have IPv6 /64 and /48 networks at all my sites, so looking to encrypt the traffic between them. This will probably apply to IPv4 networks using public IP space too?

I feel like this should be common, but my searches keep giving me examples about LAN-LAN.

Is there an example somewhere for this? What search terms should I be using?