Migrate from ZHA to zigbee2mqtt

Hi all

I am quite new to the topic, but spent quite a lot time analyzing how everything works.
But now I have a question.
Currently I am on a ZHA network with 32 devices (18 of them are ubisys devices in the wall, not easy accessible).
Now I wanted to switch to zigbee2mqtt because I believe this is the more seminal way.
I analyzed the old configuration, the PAN ID, the network key, … Sniffed a bit with zboss, and was quite sure, if I configure everything correctly on z2m, it should see all devices.

And it does if i do a raw network map. But I get these messages: “Received message from unsupported device with Zigbee model ‘undefined’” and I can’t bring z2m to find the devices without resetting them.
When I manually created an entry in database.db, it seems to work, but this is not the way to go… But I cannot understand, why there is no feature to detect all devices in the network and “interview” them, even if they are already joined. Is this a low-level feature just available on join? Because for example, deconz is able to do exactly this.
Or how could I approach this without the need of opening all the switches? What do I miss?

I am using Conbee II on ZHA but also have some CC2531 available.

Thanks a lot,