I can tell that the display is definitely in HDR mode. Unfortunately it does not look very good. The fonts are weird, as if they aren't antialiased. It is especially noticeable in black-on-white text.
Is there a way to improve the HDR mode?
The display is connected through USB-C. Changing resolution to
Default for display does not help. I have used this display in HDR mode with ChromeCast Ultra so I know how good HDR can look.