Fail to print with a USB-connected Brother QL-700

I am able to add the printer but there is no specific driver for this model (QL-700) so I can pick the QL-800 or QL-650. Both options fail anyway when I try to send a printing job to the printer.
The error is seen on the printer itself (blinking red LED) but the logs of ghostscript-printer-app don't say much.

Trying to use CUPS (no ghostscript-printer-app) to install the printer with the PPD file provided by Brother for the QL-700 works fine. But it fails as soon as I send any printing job. Although I'm getting more info from /var/log/cups/error_log:

W [29/Dec/2022:21:47:51 +0100] [Job 120] Grayscale/monochrome printing requested for this job but Poppler is not able to convert to grayscale/monochrome PostScript.
W [29/Dec/2022:21:47:51 +0100] [Job 120] Use \"pdftops-renderer\" option (see cups-filters README file) to use Ghostscript or MuPDF for the PDF -> PostScript conversion.

I tried every option below as well:

$ lpadmin -p QL-700 -o pdftops-renderer-default=pdftops
$ lpadmin -p QL-700 -o pdftops-renderer-default=mupdf
$ lpadmin -p QL-700 -o pdftops-renderer-default=hybrid
$ lpadmin -p QL-700 -o pdftops-renderer-default=pdftocairo
$ lpadmin -p QL-700 -o pdftops-renderer-default=acroread

with no success for any of them.

I also followed the development in this thread regarding a possible bug between the Brother driver and cups-filters, but that didn't help as I am not able to downgrade cups-filters on my machine.

I am running Ubuntu 22.04, CUPS 2.4.1 and ghostscript-printer-app 1.0.

I should finally mention that this particular printer with the exact same driver used to work just fine before a system upgrade. If only I could downgrade CUPS, I've got the feeling it could solve the problem.

Riprodurre un processo di stampa usando Ubuntu 22.04, CUPS 2.4.1, ghostscript-printer-app 1.0 e il PPD Brother QL-700. Confrontare i log di ghostscript-printer-app con /var/log/cups/error_log e le opzioni del renderer riportate. Il lavoro è completato quando si identifica se il problema si trova nell’applicazione, nell’integrazione con CUPS o nel percorso del driver e si documenta una correzione concreta o una limitazione.