There’s a setting to turn IPv6 on so that PMS starts listening on IPv6 (see the link of @TeknoJunky ), but that doesn’t tell the clients what the address is, which is what you really want.
In order for clients to connect to PMS over IPv6 you need to push a custom server URL to them. There’s a short explanation here: Ipv6 support for myplex - #269 by thornrag
With IPv4 this happens automatically behind the scenes, with IPv6 you (unfortunately) still have to do it manually. I wish the developers would add a simple input box “IPv6 address to push to the clients”, so we don’t have to construct the URL ourselves anymore. (Oh, and support PCP/IGDv2 for automated port opening, but that’s for another time).
