If you see Input Not Supported Monitor error on your Windows 11/10 PC, you can apply any of the solutions in this post to resolve the issue.

Dell U2312HM The current input timing is not supported by the monitor display. Please change your input timing to 1920×1080@60Hz or any other monitor listed timing as per the monitor specifications.

That is how my monitors have always worked. Whether the display is actually 'displaying' the selected input or not, the device connected on that input thinks the display is there and powered on.