I got both the open thread border router and the matter server all setup via docker and allowed ipv6 routing on the host. As far as I can tell everything is up and working. I synced the app with the router and that works. When I scan the matter QR code on the u400 it attempts to add it but then comes up after a while saying it can't be used on this network.
Not sure what's going on here as this is my first walk in the matter ecosystem