I currently have macOS Big Sur. I am trying to setup my Pixma MG2522 printer. I am getting this message:The developer of this app needs to update it to work with this version of macOS. Contact the developer for more information. What do I need to do?

The message is very clearly telling you that in order for your printer to work you need to go to Pixma's web site and download the latest print driver that is compliant with Big Sur and install it. This is a very common requirement after any operating system upgrade.

The link to the MG2522 printer drivers shows that they were released (early Oct 2020) before Big Sur beta period ended, and so may not work with the released Big Sur versions, even if Canon suggests otherwise. There is no AirPrint support for this device.

Only if the referenced Canon drivers do not work, would I suggest downloading the GutenPrint for Mac which also supports the MG2522 printer.

Here's the link: https://www.usa.canon.com/internet/portal/us/home/support/details/printers/support-inkjet-printer/mg-series/pixma-mg2522/pixma-mg2522?tab=drivers_downloads

Download and install the driver

To correctly determine if it will work, you appropriately need to go to PIXIMA's web site to see what they say will work. Using another printer's driver often will not work. One way to find out is to install it and see if it works.

This one? :

"MG2522/MG2525 CUPS Printer Driver Ver.16.40.1.0 (Mac)"

I have PIXMA MG5200 which doesn't work after Big Sur upgrade. Will the printer driver for PIXMA 2522 work on my printer?

Worked fine. Thank you.

I'm now puzzling over getting the Mac to recognise the scanner

It worked fine, Thanks!