Hi
IPv6 is disabled in OSMC by default, as many routers don’t implement it properly and it can cause problems for the user. It should be possible to get it going, however you will not be able to do this via My OSMC’s Network interface.
First, check lsmod shows ipv6 is loaded.
You will then need to manually enable IPV6 via ConnMan’s configuration file for the interface. See this resource for some guidance: doc/config-format.txt - pub/scm/network/connman/connman - Git at Google
Sam