To fix this no input signal issue you just need to change the input setting. Changing the input source Turn on the computer monitor.

If you wanted to use a computer LCD as a TV monitor, is there a cheap box that will convert a standard output from a VCR or DVD player to a VGA signal that an LCD would use?

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.

But when I switch the monitor input from HDMI1 to DP to use my PC, the monitor essentially disconnects from the laptop, and all the windows/apps move back to the work laptop.