AWStats is a popular tool that shows different reports and logs about traffic and activity on your website. On Linux servers, most of the time it comes already installed, it does not have a high quality interface and detailed reports about conversions, but is good to know better your traffic sources, visits, countries and cities, operating systems, browsers and more.
Is not focused on e-commerce, conversions or goals, but you can get useful insights about site errors, not found pages, different status codes. Is useful for technical audit for a site health.