Hi. The GeoIP module is a core module in NGINX upstream. Keeping this in mind, it's just packaged here as a dynamic module.
For reference purposes, I have forwarded this bug report to nginx upstream's nginx-devel mailing list [1] for their response. (Note that this is just me adding information, not adding anything 'new' to this discussion, as it is ultimately up to the maintainers to include a third party module or not here in Debian) Thomas [1]: http://mailman.nginx.org/pipermail/nginx-devel/2019-January/011852.html
