Thanks for your reply at Burning a USB drive with VMware ISO file - #7 by ab77 !
I tried following your instructions, but maybe I’m missing something. I was able to unwrap the payload image, and I put it on a USB. I then booted from an Ubuntu ISO to serve as my server rescue system. I plugged in an additional USB key with the unwrapped balena image.
My server hard drive is the 240GB SSD. It is all free space.
I then ran the command:
dd if=/media/ubuntu/usb_with_unwrapped_img/unwrapped_img.img of=/dev/sda bs=4M
and rebooted.