RDNA2 GPUs get a much larger performance gain than RTX30 series GPUs in Blender 3.0 Beta/Cycles X using AMD-HIP. (Blender 3.0 Beta Classroom results: RX6800XT - 20sec, RTX3080-20sec, RTX3090 - 17sec.) :
Blender 2.83: Best CPUs & GPUs For Rendering & Viewport – Techgage
NEED HELP!: GPU cycles rendering problem - Technical Support - Blender Artists Community
Blender 2.83: Best CPUs & GPUs For Rendering & Viewport – Techgage
Check out the new features in Blender's Cycles X renderer | CG Channel
Blender 3.0 takes support for AMD GPUs to the next level. Beta support available now! - GPUOpen
Blender 3.0 Will Have AMD HIP-Based GPU Acceleration - Phoronix
Radeon RX 580 issues with blender, Cycles and Eevee Render Engines : r/Amd
Accelerating Cycles using NVIDIA RTX — Blender Developers Blog
Blender 2.83 crashing on Amd gpu - Cycles Development - Blender Developer Talk