I have it all working. Solely relying on home assistant. So, OTBR,matter, thread are all installed and seems to work. I could pair the nanoleaf bulb. What was disappointing, like hue has an “effect list”, the nanoleaf bulb connected via thread has only minimal attributes.
But the main problem. Once it looses power, and the power is on again, the bulb keeps being unavailable. Reloading the OTBR made it available again.
Would be nice, there would be a reconnect. Apparently, there thread network itself was working, because I could connect to the bulb with the nanoleaf app, and turn on/off the bulb.