The official compatibility list consists of devices the staff have tested and confirmed work with a built-in driver. There is no other way to add to that list.
However there is a wiki post that anyone can edit to indicate that a device works with a custom driver (or a built-in driver, like a generic zigbee or z-wave driver).
I have been buying the Xfinity Zigbee contact sensors for years now and using them with Hubitat, with the generic Zigbee contact sensor driver.
That makes me think all their Zigbee devices will probably work with the generic drivers built into the hub. What else do you have for devices? I'm assuming at least motion sensors, and I would assume the generic zigbee motion sensor will work fine for those.
I don't know about the keypads, but I wouldn't be surprised if there is a custom driver out there that will work with them if they are Zigbee.
Hubitat doesn't do much with cameras, but if you can get an mjpeg feed from them, possibly using other camera software on a computer, then they will stream into an image tile on a dashboard.
Almost everything should work fine. I’ve got their older contact sensors, a motion sensor, and a keypad all connected to a C-8 Pro and they work for my needs.
I have been using one of these zigbee sensors (or at least one that looks EXACTLY like that) that was supposedly an Xfinity sensor with Hubitat for a few years. Works great. I like the added temp sensor it has built in. Battery lasts about 1 year on a door that is opened probably an average of 4-5 times/day.