[Solved] PiGear Nano: boot from SSD (via USB) / change boot sequence (on CM4)
PiGear Nano is a carrier board for Raspberry Pi Compute Module 4 (CM4), so it can not decide the boot sequence by itself. The changing of boot sequence need to be done on CM4.
If you have CM4 without eMMC (CM4 Lite), you can decide to boot from SD card or SSD (actually via USB), depends on which one is connected.
If you stick with CM4 with eMMC, your best bet is to boot from USB because CM4’s eMMC is also connect to SD interface and you will not be able to boot from SD card. You will need to change the boot sequence in order to boot from USB, which is unfortunately very tricky, and Raspberry Pi’s official document is not very clear on this aspect. In attachment you can find a tutorial about changing CM4's boot sequence. Basically you will need to go through the procedure for updating the firmware. Very inconvenient but this can eventually be done.