I find analytics that is not actionable in any way a waste of time. For example, checking the Insights Traffic pane on GitHub on your own repos to see how many people viewed your repo or cloned it. Or seeing how many people visited your own personal site with Google analytics. It serves 0 purpose and is only addicting due to its ego boosting nature.
For user facing products, well implemented analytics will let you see how to optimize your system to serve some end goals better and for that you need data.
Matamo - Open source alternative to Google Analytics.
LocustDB - Massively parallel, high performance analytics database that will rapidly devour all of your data.
Grafana - Tool for beautiful monitoring and metric analytics & dashboards for Graphite, InfluxDB & Prometheus & More.
Cube.js - Open source modular framework to build analytical web applications.
Analytics.js - Hassle-free way to integrate analytics into any web application.
Plausible Insights - Simple, lightweight analytics for your website.
OmniSci - Interactively query, visualize, and power data science workflows over billions of records.
Freshlytics - Open source privacy-friendly analytics software. It aims to be reliable, friendly to use and easy to deploy.
MixPanel - Analyze user behavior across your sites and apps. Then send messages and run experiments from what you learned–all in Mixpanel.
blackrock - Events & Analytics.
ClickHouse - Open-source column-oriented database management system that allows generating analytical data reports in real time.