Hi,
KoenZomers created this great backup utility for pfSense https://github.com/KoenZomers/pfSenseBackup
Ive added support for OPNSense, because Im switching all FWs to OPNsense - great piece of SW.
Now backup tool is multiplatform thanks to .NET core framework.
So this is my small contribution to community.
All credits to KoenZomers.
Do you know that there is a REST API for downloading the config file in OPNsense?
Just install the os-backup-api and you do not need to mess with the frontend. It is just a single call.
I could download mine with curl which has the big advantage that I do not need the .NET framework.If you really need to run it on Windows, I recommend to use curl on windows as well or powershell which has as far as I know an HTTP(S) client.