The next camera entry was the mighty EOS RP.  It's advantages were better light sensitivity, a wider field of view through a full size sensor, faster autofocus, preview video over USB.  Combined with the junk laptop's higher framerate, it managed real good tracking without the janky Escam.  

The preview video can be previewed by running

gphoto2 --capture-movie --stdout | mplayer -

The preview video in video mode is 1024x576 JPEG photos, coming out at the camera's framerate.  If it's set for 23.97, they come out at 23.97.  If it's 59.94, they come out at 59.94.  Regardless of the shutter speed, the JPEG frames are duplicated to always come out at over 23.97.   They're all encoded differently by a constant bitrate algorithm, so there's no way to dedupe by comparing files.

Once streaming begins, most of the camera interface is broken until the USB cable is unplugged or the tracker program is killed.  There is  some limited exposure control in video mode.  In still photo mode, the preview video is 960x640 & the camera interface is completely disabled. 

Whenever USB is connected, there's no way to record video.  There is a way to take still photos by killing gphoto2, running it again as 

gphoto2 --set-config capturetarget=1 --capture-image

& resuming the video preview.  It obviously has only a single video encoder & it has to share it between preview mode, video compression & still photos.

In video mode, the camera has to be power cycled to get gphoto2 to reconnect to it after killing the program.  In still photo mode, it seems to reconnect after taking a still photo.  The lion kingdom will probably use 30 minutes in video mode & 30 minutes in still photo mode in practical use, so a method would be required to remotely trigger gphoto2 if USB previewing was the goal.

Helas, the lion kingdom decided not to use USB previewing at all.  The next step is to try an HDMI capture board.

Added more safety features to keep the mount from destroying the camera, manely it goes into a manual alignment mode when it starts & only starts tracking after the user enables it, has limits to the step size.  Unfortunately, initialization still sometimes glitches to a random angle.

Tracking tilt continues to be a big problem.  It can be used with some kind of manual tilt control, but there should be a way to do it automatically.