Haven't found a way to check screen on time in Windows 11. In MacOS there is Screen Time which gives useful information regarding screen time, application time usage etc. Is there something that is the same in Windows?
Go to settings. Click on the system tab, then scroll down to power and battery. Click it and then expand "battery usage" section.
Here you will see a chart showing 24h battery usage of your PC. Just below this chart you will find the screen on time, screen off time, and the total sleep time.