Big Sur - Canon MX320 printer doesn't accept print jobs

Since Big Sur 11.5.1 and/or 11.6.1 my old Canon MX320 printer doesn't accept print jobs for documents. It prints color test pages, and I can scan successfully with the VueScan app.

The error.log says:

E [18/Nov/2021:23:57:38 +0100] [Client 135] Returning IPP server-error-not-accepting-jobs for Create-Job (ipp://localhost/printers/Canon_MX320_series) from localhost.

I have these printer apps in my user's Library/Printers directory:

Both printers have this strikethrough symbol, and show the same behavior.

And both printers show the same print dialogue:

... with the only selectable paper format US letter whereas the MX320 printer uses its DIN A4 paper format. Could this be the culprit?

Can I add additional paper formats, how this was possible with former MX320 printer apps, and if so, how? Or are there other means to go on with printing?