Replacing convection/microwave oven

Convection microwaves can perform all the cooking functions including barbeque your food. It provides uniform heat to the food item placed inside, making the food crispier. It is more expensive than the other two variants.
bakingreview.com

I don't believe Dometic makes their microwaves. They've rebadged other brands. Fwiw my old Dometic mw in my old trailer was actually made by Samsung. If you Google the Dometic serial number you might get the equivalent in the actual manufacturer brand

One quick word of advice. If your microwave has one side flush against the wall (usually left side) be sure the microwave you get as a replacement will allow the door to open against a flush wall. Some doors are hinged so that they need a few inches to the side to fully open.
I discovered that this past summer when I replaced my microwave. First one I purchased and installed, then when I tried to open the door it hit the left wall.
Out it came and I had to find another microwave that would open correctly against the wall.

previous RV had a GE MW/convection over the range

took it down measured it, went to Home Depot and bought a replacement
also GE

You will find many over-the-range microwaves and most have similar dimensions to yours. I just replaced ours in the S&B with this Whirlpool which has almost the exact same dimensions as yours, however it doesn't have a convection option.

This biggest problem with replacing one with a different brand is the mounting methods. If you do, be prepared to remove the current mounting plate and install a new one, sometimes easy, sometimes not.

Let google be your friend.