I have tried to get Matter integration up and running.
However, without success.
HA runs as a VM on a Proxmox.
The Matter server can be installed and, in my opinion, is running.
Only Matter integration does not want to start/is not displayed. When I try to set it up, I always get a message saying that I need the appropriate hardware.
However, my three Apple HomePod Minis are recognized in the Thread Integration. (Border Router)
When I install a new blank HA VM, Matter Integration works there.
Proxmox should at least not have an IPv6 problem.
I have read this several times in this context.
The problematic HA VM also shows me an IPv6 address.
Not sure if this is the same issue - but i had something similar getting a new ZBT-2 working. I have homeassistant running on a VM on a linux box.
I was using NAT and port forwarding for the network connectivity of the VM. Switching over to bridged mode allowed the MDNS traffic to get to Open Thread Border Service on the VM which was being blocked before.
It is easy enough to check if this is your issue. Download a free app like Discover (IOS) (nothing to do with me BTW) and look for traffic on _meshcop._udp - you should be able to see your three homepods on one network and, if it is working , your home assistant OTBR .
initially i could only see the homepods - moving the vm over to bridged mode immediately resolved the issue