I've looked at what's available in the 'matter' object, and it's at a somewhat confusing layer of (or layers of) abstraction. IIUC (and this is a big caveat, since I am no Matter expert) there is some very high-level stuff (like "matter.on()", to generate the invoke necessary to turn on a switch) and also some mid-level support like "matter.invoke()" that seems to let you conveniently do much of what Matter's invoke supports, but not all. Pushing that all into one object feels odd, like it might not scale well.
I don't see any way to do a timed request (e.g., to allow sending a lock request to a Matter lock), and I don't see how that would get built on top of matter.invoke. I've heard rumor of the very, very vaguely documented "he raw", but it's not even clear to me if that is zigbee-specific or somehow supports many or all protocols.
The "how to build a matter driver" page is really helpful and well-written. Is there any other documentation or description of the model that exists or is planned for Hubitat to support Matter? Selfishly, I think I really only care about timed invoke (I think like others, I would like to get Lock support), but more generally I think some formal description of the model and its level of abstraction would be really helpful. (I know, I know, writing useful documentation takes far longer than fixing bugs and adding features, so no slam on the Hubitat team 
