OK, a piece of follow-up. After the success with the nano, I put Jetson tx2 nx cards in slots 2 and 3. They are just the boards, so there is no microSD slot on them. I tried installing the Jetson OS (the SDK manager can recognize them because they are in slots 2 and 3) but the installs failed - I'm guessing because they have no onboard card. So I attached 1 TB SSDs to the M2. t2 and t3 slots on the back of the board, gave them a basic formatting (by moving the nano from slot 1 to slot 2 then slot 3 so I could access and format them), plugged the tx2's back in, but the install still fails. On the theory one of the boards might be be bad, I tried to flash the other one. No such luck. Not sure how to proceed, though I think I'll try flashing the SSDs with the Jetson OS.