While there are many other options for time tracking tools like Toggl, ManicTime, Time Tracking by AND Co, options for a completely free tool seem a little less. Some of these tools have a very negligible fee and also provide free versions, their free versions, however, impose some limitations on the team size. The paid versions definitely offer you a lot more features.
Another alternative to this is to get a custom tool created for your business. Although it will require some initial investment, it will basically become free over the years. Sooner or later, Clockify might start charging a fee for their services as they too will have to keep themselves afloat.
There are many good apps: Tsheets, Clockit, Atto. Our company Turtler is also going to launch a GPS app in July this year. You can also read my article "A Complete Guide to the Top Ten Employee GPS Tracking Systems" at https://turtler.io/news/a-complete-guide-to-the-top-ten-employee-gps-tracking-systems.