Hubitat Hubs do not have a local Thread 2.4GHz radio onboard. Thus, in order to use "Matter over Thread" devices, you will need some other device in your home to act as a "Thread Border Router" device. Some Apple HomePods and AppleTVs have this capability, along with some models of Google Home Hubs and Amazon Echo devices.
A Thread based device uses a 2.4GHz radio, but it is different than 2.4GHz WiFi or 2.4GHz Zigbee. Thread is its own, unique, mesh wireless protocol. Think of it as a new and 'improved' version of Zigbee.
A Thread Border Router allows "Matter over Thread" devices to be 'seen' on your home network, just like any other "Matter over WiFi" or "Matter over Ethernet" devices. It is these types of devices that can be 'seen' by Hubitat, since Hubitat does not have a built-in Thread radio.
I know this was a little long-winded, and I apologize. But it is just not a super simple topic to try to explain. I hope this helps in some way!
Edit: Maybe a picture will help. Hubitat is a "Matter Controller" in the following diagram.
