Hello,
I am not able to reproduce this.
apt update and apt upgrade
cat /etc/armbian-release: VERSION=20.05.2
sudo armbian-add-overlay sun7i-a20-can.dts works:
Compiling the overlay
Copying the compiled overlay file to /boot/overlay-user/
Reboot is required to apply the changes
Reboot, but no can0 interface with
sudo ifconfig -a
jjf@bpi2:~$ dmesg | grep can
Joachim