If you run the SkyConnect in Multi-Protocol setup, then both Zigbee and Matter must be changed and it can be a pain to change them both.
Yeah don’t use multiprotocol if possible.
the SkyConnect/Connect ZBT-1 RF gets checked in factory, a device with non-working RF would be unexpected.
I’d still suspect interference of some sort. Even longer or different USB extension cable might help, or a completely different location (for testing). The SkyConnect and the RF protocol IEEE 802.15.4 are a bit susceptible to interference unfortunately.
Update from my side:
My SMLIGHT SLZB-06M arrived today.
I set it up and configured it as Matter/Thread. It is connected via Ethernet (PoE) and working fine with Home Assistant.