Is there a free and open source benchmarking software I can use that is compatible on both Windows and GNU/Linux?
There is Blender's Open Data Benchmark tool.
Phoronix test suite has some cross platform tests in its listing (like Unigine's tests)
If Amigas were so good at rendering in the 90's, it would be cool to use UAE to render a 45 minute battle scene from Babylon 5 on a threadripper. Just to see how many milliseconds it would take. lol
That should be the new benchmark.