GFXBench is a graphics benchmark suite. A OpenGL only version (GFXBench 4) is available for GNU/Linux. There is also a version 5 for Android, iOS, macOS and Windows. GFXBench 4 has three different scene rendering tests (Car Chase, Manhattan, T-Rex) which it can test in various ways (on-screen, off-screen, etc). Detailed results are shown for each individual test. It produces scores for each individual test but does not produce any overall score for all the tests it runs.
Features And Usability
GFXBench itself is a small download. However, it will connect to a server on the Internet and download 288 MB of data. It will only download the data once but it will connect to the Internet every time you launch it.
GFXBench has a number of tests you can run and a comparison tab which lets you compare the score online. Each tests gets a score and some information about the test. There is no overall score for all the tests, you would have to compare single test scores if you want to compare one machine with another.
The "Linux Edition" download page claims "For AMD and Nvidia proprietary video drivers are strongly recommended". You do not need the proprietary driver to run this benchmark. The only tests which is not using OpenGL 3.0 is Manhattan which uses OpenGL 4.3. Mesa has had full OpenGL 4.6 on Intel and AMD graphics cards for quite some time.
GFXBench is available from gfxbench.com. The GFXBench 4.0 page has the Linux OpenGL version. GFXBench 5.0 supports Android, iOS, macOS and Windows - there is no Linux version of GFXBench 5.0 available.