Add more photos of the exterior, please. We can only guess what the entire house looks like right now.

Looks like the arched door is integral to the exterior and you need a custom door and jamb $$$$

Contact a local custom cabinet/millwork shop. They can make you what you need.

Yes, you can find a round top door with jam system. But careful on site measurements are needed.

I need to see the whole house but that IMO will be acustom job for the door

Patricia, I understood what you mean. But I figured worth getting door company to come measure and see what stock solutions might be available. Could save a good bit of money. Knotty Alder rather than mahogany also saves. Just do dark stain. I did this on a very high end home and we saved thousands really! It was double door so single door is easier and less expensive too.

Abatron.com

While growing up we had a Tudor styled home with an arched front entry door, similar to yours. I would definitely have your door replaced with a similar shaped arched door. Get some estimates!!

Is it feasible to keep the door but replace the rotting frame?