I have a HP SMART TANK 515 printer but it doesn't work with Big Sur. Any solution?

The HP Smart Tank Wireless 515 All-in-One printer is supported by Apple's built-in AirPrint, without need for HP drivers or software.

With the printer powered and networked, visit System Preferences : Printers & Scanners panel. Right-click on your printer entry and select Reset printing system… This will allow you to re-add your HP device. Instead of selecting HP drivers, choose AirPrint when you re-add the device. Print something.

Apple seems to think it is AirPrint compatible from the following bulleted item, and HP only shows one version of the Smart Tank 515 as being a wireless model:

I suppose you could install the HP Smart software for this device and see if it allows you to reset your printer and add that HP driver support.