Linux 5.9.12 Is In Good Shape With The AMD Radeon RX 6800 Series
Linux 5.9.12 was released a few days ago and I've had time to confirm on my end it indeed works fine on the Radeon RX 6800 series graphics cards. In particular, a fix from Linux 5.10 was mistakenly not back-ported to Linux 5.9 for handling newer versions of the RLC iRAM and dRAM microcode. Without that it could lead to hangs for these new "Sienna Cichlid" GPUs.
So if you prefer not running Linux 5.10 since it's not yet formally released (but should be next week) or using the packaged driver on a supported Linux distribution, Linux 5.9.12 should be in good shape. Along with the Linux 5.9.12+ kernel you will want to be using Mesa 20.2 at least (or ideally 20.3 or 21.0-devel for the best performance), ensuring Mesa is built against LLVM 11.0+, and also running linux-firmware.git for the necessary microcode files. With that combination you should be in good shape - the requirements haven't changed compared to the launch day report on Phoronix, just that now Linux 5.9 is playing nicely in the mix if on 5.9.12 or subsequent point releases.
Linux 5.9.12 has many other fixes in general as well and can be downloaded from Kernel.org if wanting to spin it up from source.