Netbox may be quite annoying if you have many devices to add. There is an ansible moule to do it, but that is not really easy either (see this thread for more informations).
Nevertheless, that is doable; see an example here.
In this repository, you will find a basic python script to export list of interfaces from a linux host device into a compatible CSV file for netbox.
Just clone this repository. You will need a python3 interpreter.
As there is only one single useful file for now, you can also just download it:
cd /tmp && wget https://raw.githubusercontent.com/remyd1/linux-local-netbox-export/main/interfaces.py
# or, with curl
curl -sO https://raw.githubusercontent.com/remyd1/linux-local-netbox-export/main/interfaces.py
python3 interfaces.py
cat interfaces.csv
Or, for a virtual machine :
python3 interfaces.py --virtual
cat interfaces.csv
Now, you can import the CSV file into netbox device interfaces.