U2713H does not have the HDR/EDR certification due to its age but it is true wide gamut 10-bit display with hardware LUT calibrated by X-Rite i1 Display Pro Monitor Calibration Device.
It is not fair to compare Affinity Photo with the professional software like Photoshop therefore I mentioned only the "NEC 10 bit Color Depth Demo application" but I also have "Adobe Photoshop Version: 21.0.2 20191122.r.57".
Photoshop has a "30 Bit Display" setting unter "Edit" > "Preferences" > "Performance" > "Graphics Processor Settings" section > "Advanced Settings..." button (look at the screenshot in attachment). 10 bit gradients like this one https://github.com/jursonovicst/gradient are smooth in Photoshop with this setting. In Affinity I do not see any difference between 8 and 10 bit gradients just like in Photoshop if "30 Bit Display setting" is disabled.
https://affinityspotlight.com/article/biggest-ever-affinity-updates-bring-unrivalled-speed-power-and-extensive-new-features/ provides only marketing information unfortunately so I still do not understand why the gradients are not smooth.
Is it possible that Affinity does not support higher bit depth on Windows?
Does Affinity Photo have an equivalent of the "30 Bit Display" setting in Photoshop?