Carlos E. R. composed on 2020-12-05 22:54 (UTC+0100):
If you google «cups says Unsupported document-format \"text/plain\"» you find hits. First one:
https://lists.opensuse.org/opensuse-factory/2014-11/msg00179.html
«google search for client-error-document-format-not-supported suggested missing cups-filters: https://lists.debian.org/debian-printing/2014/02/msg00026.html
Installed: cups-filters 1.0.58-35.6 libqpdf13 5.1.0-1.4
now Echo "Test" | lp works
AND: regular printing now works.»
That is correct, you do not have installed "cups-filters", it is not in your list. That's strange, yast should have installed that automatically.
I neglected to regenerate the installed packages list before sharing it.
# zypper se -i 32bit libstdc cups pdf
...
i | cups | The Common UNIX Printing System | package
i | cups-client | CUPS Client Programs | package
i | cups-config | CUPS library configuration files | package
i+ | cups-filters | OpenPrinting CUPS filters, backends, and cups-browsed | package
i+ | cups-pk-helper | PolicyKit helper to configure cups with fine-grained privileges | package
i+ | glibc-32bit | Standard Shared Libraries (from the GNU C Library) | package
i+ | hl5470dwcupswrapper | Brother HL-5470DW CUPS wrapper driver | package
i+ | kdegraphics3-pdf | KDE PDF File Viewer | package
i | libcups2 | HTTP/IPP communication and printer queue and job library | package
i | libcupscgi1 | CUPS web interface support function library | package
i | libcupsimage2 | CUPS library for working with large images | package
i | libcupsmime1 | MIME database file routines for CUPS | package
i | libcupsppdc1 | CUPS PostScript Printer Description (PPD) file compiler library | package
i | libgcc_s1-32bit | C compiler runtime library | package
i | libqpdf26 | Shared libraries for qpdf | package
i | libstdc++6 | The standard C++ shared library | package
i+ | libstdc++6-32bit | The standard C++ shared library | package
i+ | libusb-0_1-4-32bit | libusb-1.0 Compatibility Library for libusb-0.1 | package
i+ | mfc8910dwcupswrapper | Brother MFC-8910DW CUPS wrapper driver | package
i+ | python3-cupshelpers | High-level Python Bindings for CUPS | package
i+ | python3-pycups | Python Bindings for CUPS | package
I'm well past installing filters and 32bit packages, and I even started a
forum thread that's had three people weigh in on it so far:
https://forums.opensuse.org/showthread.php/547780-brother-IP-printers-HL-547...
Still nothing coming from the printer, due to filter failure (according to
http://localhost:631/printers/