Second you need the kexts loaded at startup using a startup item or launchd script. Again this comes with a VPN front-end, and I believe the binary installer from the URL above also sets this up for you. Otherwise, you have to load them manually each time you reboot.
Tun/tap Driver For Mac Os X
Windows Tun Tap Driver
Mac Os Tun Tap
The TunTap project provides kernel extensions for Mac OS X that allow to create virtual network interfaces. From the operating system kernel's point of view, these interfaces behave similar to physical network adapters such as an Ethernet network interface. Kernel extensions, called kext for short, are modules of code that are loaded directly into the kernel space of Mac OS X, able to run at a low-level to perform a variety of tasks. Most kexts are part of the core Mac OS X system software, typically hardware device drivers, but some third party apps will install a kext as well. Tunnelblick installs all necessary drivers (TUN/TAP) and binaries and it offers an easy-to-use GUI (graphical user interface) for the connection management. Tunnelblick runs on OS X 10.4 and higher, including the latest versions: High Sierra, Mojave, Catalina, and Big Sur.