How do someone pair a matter device which only give a 21 digits code?
Hubitat seems to be limited to 11 digits format. The Sonoff bridge-M does not provide a 11 digit code. I could pair it to HA no problem and then reshare it to Hubitat but I wonder why I could not go directly.
Are you using the Hubitat app? You should be able to scan the QR code, which actually decodes into a string like I posted, but that doesn't matter. And tell us if the Hubitat app you are using is on an iPhone or Android device.
I was not using the app properly. I was using connecting to hub and then going to add device instead of going directly to the other add device path. Doing this was feeding me the hub web interface which does not have the ability to scan the code.
I found it confusing to be offered two different path in the same app to add Matter devices with one beeing incomplete.
After light testing this hub does bridge zigbee devices as Matter devices and can also makes HA devices show as Matter devices to HE (with somewhat limited feature though)