Whitebear report is very interesting.
FYI, attached is the Whitebear report for one of my Google Chromecast dongles with BubbleUPnP server running.
The UPnP Device Type is identical to that of the NAD, as are the three renderer Services.
Is port 38400 open to MC on your router / security software? Per your Whitebear, that's where the Renderer Services are located.
Updates: Now I am not sure if your Port 38400 really needs to be open. I've attached the list of five ports used by my MC Servers: 1900 is UDP, the other 4 are TCP/IP. For sure, these are all opened in my firewall software. However this list (and my firewall software) does
not include renderer Port 55012 shown in Whitebear, AFAICT (my other Google Chromecast dongle has the same renderer Port 55012 with the rest of its address somewhat different). Since Whitebear finds and plays to your NAD, seems to me there are no issues about the NAD being discoverable on the network.
I should have mentioned: this worked fine on a previous computer running a previous version of MC. No issues at all with the NAD not appearing as a DLNA renderer. So, something seems to have changed, either in Windows 11 or in MC.
"Silly" question - have you power-cycled the NAD and rebooted computer?
Try setting up router to use fixed IP addresses for all devices on the LAN (LAN setup address reservation), rather than DHCP for everything.
As a test, can you re-install previous working version, side-by-side with MC30, then restore previous version from one of its backups? If that still works, it eliminates Win11 and current state of the NAD from the equation. Then maybe try restoring MC30 settings from the same backup. Always reboot computer and power-cycle the NAD when trying stuff like this.
You can always install BubbleUPnP Server - it's quick, easy, free, works out of the box for me with MC. Maybe that will reset something in your system, and then you can always shut it down, even uninstall it if no longer needed.