To change the macOS Big Sur login screen, locate the lockscreen.png file in /Library/Caches/Desktop Pictures and replace with your own image.
One of my all-time favorite things with Windows is how easy it is to lock the screen. You simply press the Windows key and L. With that, your screen is instantly locked, keeping your secrets and browsing history safe from unwanted prying eyes when you are away. The key combo makes such perfect sense too - Windows Lock, lock Windows. However, what if you are on a Mac? How do you lock screen in macOS?