Updated my Apple Watch Ultra (v1) to WatchOS 10 last night, and the new Modular Ultra face is available and works really well.
Because Apple didn't go into specifics on it, I will. It's got a big Time area, a big Complication right below that, six (!) little Complications (3 top, 3 bottom), and several choices for the "bezel": None, Seconds, Depth, and Elevation.
It's real good, and does a great job using the full screen of the Ultra.
The biggest change I want now for the Ultra is a black case. Maybe next year.