How to add Airport Express to HomeKit ?

Hello all,

It's exceptionally awesome that Apple has updated the firmware to enable AirPlay 2. However, after I've updated my router, I can't seem to add it to HomeKit. I can see the router in Apple Music and stream music to it. But I can't add it to a room (or otherwise discern that it's been "modernized"). I've restarted the router a couple of times, but that doesn't seem to make a difference.

On my iPhone, I go to "Home", then to the Room where the audio is delivered from this router, then "+" and "Add Accessory" (and see nothing representing the router) and select "Don't have a Code or Can't Scan". When I do see the Airport Express, when I select it to add to the room, I get an error "Couldn't add Accessory".

What's the secret??

thanks