Boot from an SD card

I have the Edge-V. The software on the eMMC and the SPI flash are untouched by me. I have one of the “generic” Ubuntu images installed on an SD card. How do I boot from it?

Disconnect the power supply, insert the SD card, access the power supply, and press the Function Button three times within five seconds.Will boot from SD card.

Is U-Boot or the boot ROM performing that process?

@Melab

The switching process is performed by the hardware.

Suppose that the firmware you mentioned supports Edge-V. The method I described will work.