HP Photosmart Plus All-in-One Printer - B209a

Wait for what, HP will not develop a driver for your printer and macOS Big Sur.

They last supported that printer with Mavericks 10.9 and the last update for

it was released in Jan 2014, 7 years ago.

You will need to buy a new printer.

Why did you write in your first post,

"My OS is listed in the HP list of drivers."

When clearly it is not.

Are you sure your printer is supported by HP in macOS Big Sur.

I went to the HP support page and it immediately says unable to find drivers for your product..

Clicking on manually select OS and you will see that the printer was last supported in Mac OS X Mavericks 10.9.

Which OS did you last use this printer with, and where do you see that it is supported in macOS 11.2

... and that is the problem. HP would have to provide a driver for macOS Big Sur to use this printer with this Mac. Apple does not develop these drivers. If HP does not have one, then either you will have to wait until they do, or use another printer that is Big Sur compatible.

Do you see any error messages when you attempt to print? Regardless, what have you tried, so far yourself, to resolve this so that we don't try offering potential solutions that may not have already worked for you?