Steps to repro:
- Create a new URP project
- Set the Build Target to iOS
- Create a reflection probe
- Bake the Lighting (click the 'Generate Lighting' button in Lighting window)
- Go to the Player Settings and choose Linear Color space (Other settings -> Rendering)
- Switch the lightmap encoding quality (Player Settings -> Other settings -> Rendering) back and forth between Low Quality, Normal Quality and High Quality

The ReflectionProbe-0 preview icon in the right panel of the project window will refresh, note how it is too bright compared to the preview in the inspector window.

Unfortunately the bug is not 100% reproducible since the rendering of the preview icon is not always called from a worker thread.

Note:
- On Windows 10, changing lightmap encoding quality to Medium, previews in the inspector and project window turn bright.

This issue happens because of the Playersetting is not synced properly across the processes.This is a known issue.

Thumbnails are rendered in *asset import worker process* in {_}CubemapPreview::RenderStaticPreview(){_}. In which it access _PlayerSettings.colorSpace_ in _CubemapPreview::RenderCube()_ function.