Are HP deskjet printers model 2540 compatible w/ Big Sur

Hi,

Yes, an HP DeskJet 2540 All-in-One is mentioned in About AirPrint - Apple Support as a model supporting the driverless AirPrint technology. An AirPrint printer is compatible with macOS (Big Sur), providing that a network connection is used. The printer and the computer must be connected to the same network (Wi-Fi router).

Reset the Mac printing system to solve a problem - Apple Support

Add a printer on Mac - Apple Support

Also answered in your duplicate post

https://discussions.apple.com/thread/252945931

You're welcome!