I cannot say for sure. The interface was quite unstable so I started going to the logs to determine why and alas they have been rotated too swiftly for me to tell
IPv6 isn’t fully implemented / supported in PMS yet.
It’s being worked on now.
If the ISP provides IPv6 only, your best bet is to run an IPv4 LAN, with IPv6 disabled in Settings - Server - Network because none of Plex’s servers use IPv6. IPv6 buys nothing at this point except difficulties.
We don’t all live in the 1970s. IPv6 works fine with PMS, about 50% of my streams are over v6. The Plex authentication servers not supporting v6 is mostly unrelated because when configured correctly at DNS and with a “custom server access url”, Plex clients can prefer v6 and connect directly to the server through that.