BPI-M2 Ultra have support 8G eMMC flash on board by defaults.for customization user , we can add 4-64G emmc on board.
So, you can burn your image to eMMC flash and boot from eMMC flash.
How to burn Android image to eMMC
please read this book：
2.2.1 How to burn android image to eMMC
How to burn Linux image to eMMC
please read this book:
2.3.1 How to burn linux image to eMMC
the first boot is from microSD card. if you want to boot from eMMC flash ,please remove microSD card from BPI-M2 Ultra microSD card slots.