Same problem with my 5120x1440 Samsung CRG9. Tried different cables and doesn’t wake form sleep.
For me it is fixed by setting DisplayPort version to 1.2 but then it uses chroma subsampling instead of rgb (so blurry texts/colors)
For me it is fixed by setting DisplayPort version to 1.2 but then it uses chroma subsampling instead of rgb (so blurry texts/colors)