RockPro64 on -current: lookup sd0a:/bsd failed

[Simon Penrose]

I have a PINE64 RockPro64 v2.1 board on which I am trying to boot -current (built 2020-09-22). I booted into the installer from an SD card and successfully installed all packages onto an external USB 2.0 SSD (Samsung Portable SSD T5) by following https://github.com/krjdev/rock64_openbsd. I removed the SD card, rebooted, and got as far as the following lines after repeated attempts:

   bootfile: sd0a:/bsd
   boot device: lookup sd0a:/bsd failed
   root device:

If I press Enter, all I get is:

   use one of: exit dwge0
   root device:

Is booting from an external drive supported or do I need to install onto and boot from an SD card? Serial log attached.

Thanks,

-s