Installing Manajaro-ARM with KDE desktop to my Pinebook Pro using the manjaro-arm-installer utility with BTRFS for the root filesystem causes a failure to boot. The error is that /sbin/init is not found. This does not occur when I choose Ext4 (F2FS was not tried).
Problem Solved: the flags for the sub-volume were missing from the bootloader config file. The installer does not add this flag when installing on BTRFS.
In file /boot/extlinux/extlinux.conf,
on line 4 (line starts with APPEND),
add rootflags=subvol=@ after the UUID of your root partition.