Hi, John H. Noel!
Welcome to the Microsoft community and thank you for asking your question in the community!
According to your description, I understand that you want to use a monitor to connect to your PS5 and display the video signal of the PS5, but your PC now uses Win + P as a duplicate screen to display on the monitor.
It should be noted in advance that both PC and PS5 are equivalent to independent signal sources. If your monitor wants to display this picture, you need to use separate connection cables to connect your signal output devices respectively, and then you also need to manually select the signal source (usually a button) on the monitor settings.
If you are not sure, you can refer to the manual of the monitor to manually set the signal source.
If you are not sure how to do it, there is a simple way. You can connect the monitor to your PS5 separately, and then the monitor will generally automatically detect the signal source, so that the signal picture of the PS5 will be directly transmitted to the monitor.
After you are not using the PS5, turn it off, and then switch the connection cable to the PC, so that your monitor will display the video signal of the PC.
Please let me know if I have misunderstood. Tell us the results and we will get back to you as soon as possible. We look forward to hearing from you. Thank you for your understanding and support!
Best Regards,
Yang.Z - MSFT | Microsoft Community Support Specialist