This will sound crazy, but I wonder if the TV could be mounted on the ceiling right above the door, using a mounting bracket that swings down to position the TV in an upright position.
OK, here are the dimensions and a little description of that space in my rig:
The cabin ceiling slopes up in a curve from the door inward to the
Main part of the cabin. There is 36" clear between the front cabinet and galley side, across the door opening. The doorway itself measured 26" wide at the door shade valance above the door, and the valance itself is about 5" deep.
From the bottom of the fixed cabin step to the overhead is 73". 68" from the floor surface at the top of the step to overhead directly above. 60" from floor at that point to bottom of shade valance.
The diagonal measurement across the sloping part of the ceiling in the entrance is about 18". This might be the critical dimension as far as
Mounting a tv goes.
I think you would need a pullout, tilt and swivel mount to have any chance of positioning the screen to be visible from both front seats and dinette.
Depending on how tight you could get it to retract into that wedge-shaped area under the diagonal ceiling, you might wind up having to duck under it in the entrance going in or out.
Hope this helps. My vote is still for a projector!