OK, I’m chalking this one up to a careless install. I’ve taken the time to reinstall Windows 10 & NRR, and I’m back up & running. FTR the issue was that I’d borked my ESP partition. Once I’d successfully reinstalled Win10 (& reformatted its main drive) I was able to successfully navigate the NRR installation & get things back into shape.
I’m currently recovering my user folder from backup & should be good to go in short order.
Thanks very much for your assistance & insight!