Solved. Sort of. The "solution", as suggested by a customer service representative was to delete the rental property and re-enter the information for 2021. This had the unfortunate side effect of unlinking the property from the history stored in Turbotax's servers about purchase date, price, land value and so on.
However, I am thankful that I can submit the return but the problem is on their side. If you bring up the browser's Developer Tools and look at the Network traffic, one of the requests is called "submit" and it gives a 200 HTTP status code indicating it received the response content from the server, not a 304 that tells the browser that it can use the previously sent information. No clearing of cookies or using a different browser will overcome a server-side error.
