I haven't been able to add a standalone Matter device to my eisy yet, but I did have some success onboarding my first device through the Shelly Matter gateway to control some RBGW LED strips.

I noticed a new version of UD Mobile for IOS was available through TestFlight (v1.2.3) a few days ago. I wasn't successful trying to enroll a Kasa Matter Plug, but I scanned the onboarding QR code for a Shelly Matter gateway I built on a Raspberry Pi and it quickly loaded entries for all my LED strips into the Admin Console.  

Most of the entries that showed up don't seem to have anything on the display panels with the exception of the On-Off switch entries, which do work as expected. I was also able to put a bunch of the devices into a scene so I could turn them all on or off in one step. Hopefully the ability to control color, brightness, and effects will be added over time, but this is a start.  

In any event, it's nice to to see some real Matter devices showing up in the Admin Console. 

Edited April 6Apr 6 by dwengrovitz

I had a similar result with Hue bulbs that are configured as Matter devices in Google Home. I used the sharing code provided by Google Home and all the Hue bulbs got added in IoX as Matter devices, all in one shot.

Now we have three ways of configuring Hue bulbs: with the Hue plugin, as zigbee bulbs without the Hue hub, and now as Matter devices.