Unsuccessful recovery or firmware downgrade (RBR20)

Ah damn. Since your warranty is out, you can open it up and find the uart serial pins and connect them to a computer with a uart serial to usb connector. Then you can open up a terminal and run the screen application against it. Available in MacOS and linux at least. And there you can see the startup output and attempt to piece together where things are going wrong. This of course is a lot more involved. But if you're up for it, I can detail where the pins are and what pins are what. I did this the other day and documented the steps.