This was my experience with Nanoleaf bulbs and the Moes Matter Bridge. So I would retry directly connecting them to the Moes Gateway. Another option would be to connect them to your SmartThings system first.
Matter over Thread Update.
I have paired a NanoLeaf Essentials Matter over Thread smart bulb to the Moes Gateway.
First I updated the firmware in the NanoLeaf app via Bluetooth. Then I tried to connect it to the Moes Thread radio via the NanoLeaf app with NO luck.
I then tried directly pairing it with the Tuya app and Moes Gateway and that was fast and easy. In the Tuya app I generated the needed Matter code and used it for pairing with SmartThings with no issues. I have a SmartThings v2 hub which lacks a Thread radio.
So the Moes Gateway acts as a Thread Boarder Router (TBR) and allows you to use Matter over Thread devices with the older SmartThings v2 hub
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