LOSS OF WIDE SCREEN USE ON MY MACKBOK AIR O.S. MONTEREY
MY OLD MACBOOK AIR SUDDENLY IS NOT SHOWING A FULL SCREEN WHENEVER I CLICK TO WIDEN MY VIEWS. WHY IS THIS SO?
MacBook Air 13″, macOS 12.7
Use apps in full screen on Mac - Apple Support
The DuckDuckGo browser app supports full screen mode. I don't know of any apps that don't.
Websites are not relevant.
In the very distant past the green button behavior was up to the app developer. It's been "Enter Full Screen" for a long time.
If it's not working as Apple describes in that document, please determine if the same problems occur in "Safe Mode": Start up your Mac in safe mode - Apple Support. Some non-Apple system modification may be responsible, though I am not aware of any that could circumvent such a fundamental Finder feature.