The cli documentation says that in config-ap mode one can enable ipv6 with 200.7 unleashed firmware. (
I have a R510 (126.96.36.199.92) and ipv6 is no recognized command. According to the cli guide, the command would be
"ipv6 enable mode auto"
I was a bit dejected to learn that Unleashed doesn't work with IPv6, but in fact, I find that with 188.8.131.52.278, it "mostly" works. As long as I do not activate client isolation on a WLAN, clients on the WLAN work fine with IPv6. Even if assigned to a VLAN. Of course, the management UI / ssh are also IPv4 only as are any L3 ACLs.
This is without activating any command through the CLI. I am guessing this is because the packets are just passed along at L2, so the AP is blind to IPv4 vs IPv6.