We're in the same boat. Just settled on the URL25 a couple weeks ago and found out there's none to be had. Would like to crawl on one before committing for a build slot. We're RV newbies but long time boaters so familiar with some of the equipment and issues.
Actually the Rear Lounge Unity only got on our radar once we saw the 2021 changes - especially the new galley layout. Bigger drawers and countertop extension. Once the wife saw that, she ruled out our previous favorite - the Unity Twin Bed.
I see the 2021 Wonders (RL & TB) also have that new galley, but I have big concerns with the overhead air handler in the rear and no ducts. The Ford gas vs Merc diesel issue is a coin flip. I probably could live with either. But since the Wonder RL can't be equipped with auto levelers, that rules out the WRL regardless.
So looking for a Florida dealer who has any of the new LTV lineups to examine and hopefully drive. Till then, the search is on hold.
BTW, if you're looking at a 2021 RL, the two jump-seats also have seatbelts. Dean makes the point many times in the videos. Legal for 4 passengers.