I've received the NanoPi M4 V2 today.
I tried Armbian images for the M4 on SD and eMMC. None boot.
So I tried the RockPi4 images since that's got lpddr4 too. That works. Of course no on-board wifi since another chip.
So my guess is the lpddr4 isn't supported by the uboot for the M4.
It is a nice board. I've got the metal case with NVMe hat too. Looks all very nice. But a bit impractical if you need to acces eMMC.