RBR50 router appears to be bricked after factory reset

> [...] I cannot get anything other than a flashing white ring on the
> RBR50. [...]

   You may be a candidate for the TFTP recovery scheme.  See, for
example:

      https://community.netgear.com/t5/x/x/m-p/1622096#M102004

> [...] I set my ethernet adapter [...]

   That's part of the TFTP scheme, so you're on the way.  (It's critical
if the router is dead enough that its DHCP server isn't working.)

> [...] I've seen many posts/docs [...]

   Thanks for the helpful links.

   My Orbi experience/expertise is nil, but if the flashing lights don't
match the published descriptions, then you might want to do some
experimental variation in the timing of the "PUT" command in the TFTP
procedure.

> [...] I have tried all 3 ethernet ports [...]

   Any of the LAN ports should work as well as any other LAN port.