Searching the forum will give an explanation, sometimes Google is your best friend.....
For short, replace "sudo armbian-add-overlay spi-h6-mcp2515.dts" with the following commands:
dtc -@ -q -I dts -O dtb -o spi-h6-mcp2515.dtbo spi-h6-mcp2515.dts
sudo nano /boot/armbianEnv.txt
insert the line: user_overlays=spi-h6-mcp2515
write and exit nano
sudo mkdir -p /boot/overlay-user
sudo cp spi-h6-mcp2515.dtbo /boot/overlay-user/spi-h6-mcp2515.dtbo
Reboot the OrangePi 3 and continue with check if the MCP2515 is recognized
John Henry reacted to BertHav in MCP2515 CAN bus user overlay