While attempting to troubleshoot issues with MDNS repeater not working with my Chromecast devices, I put together a Python script that forwards MDNS requests between two interfaces for IPv6. This can run alongside UDP Broadcast Receiver or MDNS Repeater, both of which only support IPv4. This is entirely built using ChatGPT.
So far, it seems to be working for me, though it's too early to say if this permanently fixes my MDNS issues.
https://github.com/agreenbhm/mdns_repeater_ipv6
There is already project build from scratch to support IPv6.
https://forum.opnsense.org/index.php?topic=48150.0