The latest AMD Radeon RX 6000 "RDNA2" and NVIDIA RTX 30 "Ampere" graphics cards were tested based on the cards I have available.
Off an Ubuntu 21.04 install, on the NVIDIA side was the NVIDIA 465.31 latest driver while on the AMD side their newest open-source stack is made up of using Linux 5.13 Git and Mesa 21.2-devel via the Oibaf PPA.
The AMD Radeon RX 6000 and NVIDIA GeForce RTX 30 series continue having quite healthy competition under Linux... It's amazing how far the open-source AMD driver stack has come in the past few years when it comes to performance. Granted, the RADV open-source Vulkan driver stack nor AMDVLK do not yet support Vulkan ray-tracing, but aside from that tend to be in fairly good standing. If looking at the geometric mean across a variety of Linux native and Steam Play (Proton) games:
Continue seeing all the individual Linux gaming benchmark figures for these graphics cards as well as various GPU power consumption / perf-per-Watt figures via this OpenBenchmarking.org result file . From there you can also generate your own performance-per-dollar metrics and other analysis from our open-source benchmarking software.