Matomo

Matomo is the most established open-source Google Analytics alternative, and its core pitch holds up: full data ownership, no sampling, and GDPR-oriented controls, all on a commodity PHP and MySQL/MariaDB stack that most hosts can run. The free GPL core is a real analytics product, not a demo. Two caveats matter for self-hosters. First, several of the headline extras that make it look like a Hotjar replacement, namely heatmaps, session recordings, A/B testing, and funnels, are paid premium plugins rather than part of the open-source core. Second, at meaningful traffic volumes the database grows quickly and report processing gets heavy, so the 4/5 difficulty is earned; you'll need to tune MySQL and set up archiving cron jobs to keep it responsive. For teams that want ownership and are willing to operate a database-backed PHP app, it's the default choice.