A while ago I had jool ( https://www.jool.mx ) working well on an IPv6-only test vlan. Unfortunately since then my firewall's kernel has gone through a few new versions so I needed a new kernel module. Jool version 4.1.7 utilities builds very cleanly, but I can't get DKMS to build kernel modules without various things not found. Not had the time to fix it yet, but routers which use linux, or openwrt, should be able to use JOOL.
It appears that jool should work on pfSense: https://forum.netgate.com/topic/158084/how-to-setup-nat64-using-pfsense-with-jool which suggests that BSD based firewall/routers could use Jool.
