This is a paid asset, but now you can download Automatic Quality FPS – Unity Auto-quality Free.
Detail this asset from Unity Store: Original Link
Automatic Quality FPS – Unity Auto-quality v1.0.3 (Latest version)
“If possible, please buy the package to support the developer”
Automatically adapt image quality according to frames per second (FPS) on all devices.
Easy, just drag the prefab in your scene and it will choose the best quality level at runtime.
Script is changing the level quality dynamically, during gameplay.
Added the possibility to stay on the most used quality level after some time.
All code is fully commented / explained.
* Boat scene not included
Automatic quality FPS is currently used in Douarnenez VR app store .steampowered.com/app/656770/Douarnenez_VR/