[cups] Printer not usable from command line, "Filter failed"

[Jarvis Wyatt]

Hello!
I have a Ubuntu 20.04 LAN host running cups, which I didn't
install intentionally, so maybe it was a dependency of another package.
In the same LAN, I have the printer Brother MFC-L2710DN with its own
local IP address. I can successfully print from a program with a GUI
(pdf reader, or similar). I can't print, instead, from the command line.
Some information: for some reason, the printer is listed two times and
I have no default printer set.

$ lpstat -p -d
printer Brother_MFC_L2710DN_series is idle.  enabled since tue 23 jun 2020, 10:42:41
        Printer disappeared or cups-browsed shutdown
printer MFCL2710DN is idle.  enabled since mon 22 jun 2020, 19:25:12
no system default destination

If I try:

$ lpr -P Brother_MFC_L2710DN_series somefile

it gets queued and never printed: I attach the output of `lpstat -t'. The
only error I could find is through the cups web interface (Administration
-> Manage printers -> Brother_MFC_L2710DN_series): my attempts with
`lpr -P' are listed as

Brother_MFC_L2710DN_series-12  	Unknown  	Withheld  	4k  	1  	stopped
"Filter failed"

Brother_MFC_L2710DN_series-14  	Unknown  	Withheld  	4k  	1  	stopped
"Filter failed"

Brother_MFC_L2710DN_series-16  	Unknown  	Withheld  	4k  	1  	stopped
"Filter failed"

I also attach the /var/log/cups/error_log portion related to one of
these jobs.
What could it be the problem?
Bye!

Jarvis