When you do gdisk -l /dev/mmcblk1  or fdisk -l you can se that the partition table that armbian is using is MBR (dos).   Is any particular reason for this?  When you go to the new and improved firefly rk3399 manual page you can see it is making problem when flashing through USB-C cable and upgrade_tool v. 1.24 and v. 1.34 (GBT friendly)  http://wiki.t-firefly.com/en/Firefly-RK3399/flashing-notes.html  .       

1 hour ago, denni_isl said:

the partition table that armbian is using is MBR (dos).   Is any particular reason for this?

Simply because all Armbian images works with MBR, there is no reason to use GPT yet ...

Fair enough.  Here are some good explanations about the difference between GBT and MBR https://unix.stackexchange.com/questions/120221/gpt-or-mbr-how-do-i-know  and https://www.linkedin.com/pulse/whats-difference-between-gpt-mbr-when-partitioning-drive-tiwari  This might also be of interest from firefly rk3399 manual http://wiki.t-firefly.com/en/Firefly-RK3399/type-description.html   

 

39 minutes ago, denni_isl said:

Fair enough.

I don't see any reason here to switch from MBR to GPT, unless you need partition size over the 2TB limit imposed by MBR, which is rarely the case with small SoC boards.