You can play the test patterns off a usb stick plugged in an external UHD player, which is connected to the TV via HDMI. All external HDMI sources allow Game picture modes.Since there is no way to measure Shadow Detail in Game PM, you want to set all the user parameters the same as HDR Cinema or your equivalent SDR PM so the Shadow Detail should be the same or close enough. So that said, just recalibrate your game modes. At some point i'm sure someone will figure out how to measure Shadow Detail in Game mode so you can then you can verify.
Similar to Saiyanzzrage's approach.