I have had success running a hybrid IPv4/6 network by reading this guide for inspiration:

https://blog.infected.systems/posts/2024-12-07-building-an-i...

This allows me to have a mixture of both protocols and even some boxes that have both IPv4 and IPv6 addresses. I still have some issues writing routing rules that does not fail for link-local addresses, but the network has now been fully operational for well over a month.