Help with GeoIP and csv format

[ChrisC]

Hi everyone,
I just learnt of this service: https://ip66.dev/ which purports to be a drop-in replacement for the MaxMind service.
I downloaded the mmdb, and using mmdbinspect against it works fine.
There exists a github project to convert .mmdb files into .csv files, but I have no idea if this would be compatible.
Does anyone know the format of the CSV files that OPNsense will accept for the GeoIP function?
I assume it also has to be compressed? I have seen both .zip and .gz extensions mentioned in URLs.

Thanks!