Last check in 2020 the was no tun/tap for Big Sur. Tunneling is done with another app and it doesn't work well over wifi or ethernet with classic Macs. Therefore, to be able to test Netatalk development like you want to do, you can use a real Mac or emulate a Classic Mac with Basilisk II or Sheep Shaver with an older host Mac that has the ability to run tun/tap on a host OS from 10.6 to 10.10. All the information is documented on how to do this but I'm afraid your MBP is too new or at least the OS is. Keep checking though on emulation forums as builds and documentation are released frequently. I find Cat_7 to be a wealth of information.
With today's security concerns it may be impossible to tunnel thru a network port considering that may be a seen as a security breach. Specific authorization is needed for the chip to allow it.