The good news: HDR works without the layer.
@aplattner:
The bad news: this driver has the same bug as the new GRD 595.71 on Windows, which was fixed in Hotfix driver 595.76:
When the graphics card is overclocked, GPU voltage may become capped, preventing it from boosting to expected levels [5934973]
590.48.01-6: 3135 MHz
595.45.04-0: 2970 MHz
Please ignore that the scene is not the same, it doesn’t matter.