First, you need the linux-headers for your kernel. I spent a long time searching the net before finding a .deb in /opt. Try to install the .deb sudo dpkg -i linux-headers*deb. Likely some things will be missing. I had to install the obvious and also lirc. Finally the deb will install.
Now get tun.c and compile the module tun.ko
Go to https://github.com/orangepi-xunlong/linux-orangepi and click your exact kernel under branches (see uname -r)
Navigate to drivers/net and click the file tun.c
Copy the raw link and use it in place of URL below.