I actually created a small self-hosted analytics tool myself, but it's more for qualitative feedback during the early days of the product and it's missing a lot of features that Google Analytics (for example) offers, it's more like a self-hosted Hotjar. I like using it from time to time to see if there's something wrong with a specific page or functionality. You can check it out here if you want, but it's not open source https://www.usertrack.net/