[TeMPOraL]

There are tools for analyzing server logs. I played with a CLI tool for that, but here's first result for regular folks from Google search on "server logs analytics":

https://matomo.org/feature-overview/

[icebraining]

Matomo is the new name of Piwik; it's self-hosted, but JavaScript based, not just a server log processor.

[TeMPOraL]

Apparently you can use it for just server logs; see: https://matomo.org/faq/log-analytics-tool/#faq_16303.