Hello, RVX
Welcome to the Microsoft Community.
Thank you very much for your feedback. I have carefully read the information and problem description you provided.
I understand the problem and what you are looking for.
If you set the display method of the screen to extended, this seems to meet some of your needs. After setting it to extended, your second screen will only display your desktop wallpaper, but other screens cannot be frozen. If you need to display other screens on the second screen, unfortunately, this is not possible. Windows does not provide a direct "freeze" function for the screen content of the external monitor.
As far as I know, there are some third-party software that can meet your needs, but due to the rules of the forum, I cannot provide the names of these software. You can search for related content on Google to find them.
I hope this helps you. Wishing you and your family a Merry Christmas filled with joy and warmth!
Best regards
Brian - Microsoft Community Support Specialist