Plex won’t autodiscover and auto-register an IPv6 address with the Plex cloud.
But some clients do work with IPv6, if 1) the server has an IPv6 address and 2) the client has an IPv6 address and 3) you figure out and manually configure a Custom server access URL in PMS.
Ipv6 support for myplex - #269 by thornrag
If the Plex server has an IPv6 address it might be worth trying. I’m not sure what T-Mobile Internet provides. Does it get an IPv6 address? https://ipquail.com/
