I am starting to become an expert at installing myself, due to my own problems with this board. Or more specifically the lack of decent OS to put on it, as everyone seems to have it’s own set of bugs.
I may however have a solution for you, based on my own experiences with installing debian which I prefer, but is similar.
in order for this to work you may need a PC handy preferably running another linux distro, I use mint, but any should do.
on this pc, I would suggest you install the BPI tool needed to recompile the kernel, which will be necessary after you have upgraded. follow instructions here for installation: https://github.com/BPI-SINOVOIP/BPI-M4-bsp
Before you do anything, check you can SSH into the device from a PC.
I think what you will need to do install the ubuntu image to your SD the usual way, run apt update / upgrade commands, go into the software manager and change setting relating to upgrading, to allow the upgrading process, then run the apt distupgrade command. for simplicity, I would carry out all these commands directly within the OS, not via SSH, as if a reboot is required during the installation, it may corrupt the process.
After you’ve upgraded, reboot the device, if your screen is black, but the green light is flashing, and possibly also blue, then your os is functional and its just a display problem, you should be able to confirm this by SSH into the device.
remove the SD, mount it in your PC, then use the BPI BSP tool I provided a link for to flash the old kernal back to the device, you will need to carry out options 1 5 7, you will need to mount point for the process, if you have gparted, this will confirm what this is, mine is /dev/sdi but your’s might be different.
if all goes well you should have the latest ubuntu, running on with the previous kernel. You may need to block upgrades of the kernel, otherwise the next update, may attempt to reinstall it.
This is the most advise I can offer, you will need to put a little effort into researching some of the things I have mentioned if you re unfamiliar, but if your persistent, you will succeed. like I have running latest debian doing the same process.
I hope one day someone brighter than me, will compile a more recent kernel, but I am not banking on it happening.
let me know how you get on.