Plausible is great (I use it at Sentry), but I want to clarify that only Plausible Community Edition is open source, and it note it differs significantly from their paid SaaS offering:
It makes sense, otherwise their business will be at risk.
For my analytics platform [0], I chose to go only with a paid self-hosted version. This way, the business model is aligned with the success of the self-hosted product. It's also nice to be able to provide support for self-hosting, to those who need it.
https://plausible.io