Hi @rozhok ,
you will have to build the Zynthian software by your own using as starting point the minimal Armbian debian buster image.
(You have to scroll down at the bittom of the page ti find the download link).
Then you have to follow all the steps as mentioned in the setup script (and all the others scripts that are called by the setup script).
Some adjustments are needed (remove some specific raspberry pi stuff like firmwares) as in the envars file where compilation flags have to been changed.
I’ve managed to achieve the process on NanoPi K1 (Allwinner H5 soc with 2Gb ram +32Gb emmc) a couple of years ago. It was a really long and hard way mostly because of the lack of computing power.
RockPi 4 is much more powerfull and is well supported by Armbian I guess.
Suggestion : in the setup script you’ll see a bunch of
apt install …
Make this in first.
Then do all the software download/compilation process (more or less the receipes that are here).
Make a disk image of your drive !
Then lastly apply all the patches that alter system configuration and start up scripts.