bpi-bootsel /usr/lib/u-boot/bananapi/bpi-m2u/BPI_M2U_1080P.img.gz
/usr/lib/u-boot/bananapi/bpi-m2p/BPI-M2P-1080P.img.gz

Disks: (lsblk | grep disk)
mmcblk0 179:0 0 28.8G 0 disk

Disks: (fdisk -l | grep Disk | grep bytes)
Disk /dev/mmcblk0: 28.8 GiB, 30908350464 bytes, 60367872 sectors
root@m2berry:/# bpi-bootsel /usr/lib/u-boot/bananapi/bpi-m2u/BPI_M2U_1080P.img.gz
Warning: Try to write to BOOTDISK /dev/mmcblk0
INFO: /dev/mmcblk0 : SD/eMMC !!
umount device: /dev/mmcblk0
umount /dev/mmcblk0p1

##########################
# Burning the bootloader #
##########################

sudo gunzip -c /usr/lib/u-boot/bananapi/bpi-m2u/BPI_M2U_1080P.img.gz | dd of=/dev/mmcblk0 bs=1024 seek=8
sudo: unable to resolve host m2berry

102392+0 records in
102392+0 records out
104849408 bytes (105 MB, 100 MiB) copied, 33.2562 s, 3.2 MB/s
sudo: unable to resolve host m2berry
OK!! You can reboot the system now!!

bpi-bootsel /usr/lib/u-boot/bananapi/bpi-m2u/BPI_M2B_720P.img.gz