Sorry it took so long to see that I had a response. I do have native ipv6 support.
I am still having issues when using ipv6 of my network (fiber 1gig down and 1 gig up) getting any faster performance for the download speeds.
I have assigned ULA addresses and that breaks the connection with ipv6.
I am running asus merlin ac5300 and pihole on a ubuntu 18.04 server
Let me know if you have any thoughts around this.