I did so and now .....perfect, Pedro! No more error messages from Brother drivers. Thanks a lot.

I'm glad to know. Happy to help

Changing to ATTR now brings again one error message less than before:

[    5.028777] udevd[461]: unknown key 'SYSFS{idVendor}' in /etc/udev/rules.d/60-brother-libsane-type1-inst.rules:14
[    5.028904] udevd[461]: invalid rule '/etc/udev/rules.d/60-brother-libsane-type1-inst.rules:14'
[    5.073976] udevd[461]: starting eudev-3.2.7

Time to change syntax in 60-brother-libsane-type1-inst.rules too.

[    2.607622] udevd[132]: starting version 3.2.7
[    2.610145] udevd[133]: starting eudev-3.2.7
[    5.010561] udevd[461]: starting version 3.2.7
[    5.025778] udevd[461]: specified group 'kvm' unknown
[    5.028777] udevd[461]: unknown key 'SYSFS{idVendor}' in /etc/udev/rules.d/60-brother-libsane-type1-inst.rules:14
[    5.028904] udevd[461]: invalid rule '/etc/udev/rules.d/60-brother-libsane-type1-inst.rules:14'
[    5.073976] udevd[461]: starting eudev-3.2.7

udevd[459]: unknown key 'SYSFS{idVendor}' in /etc/udev/rules.d/60-brother-brscan4-libsane-type1.rules:9

IMHO, Brother has not changed the syntax of these files:
http://www.planet-libre.org/index.php?post_id=10937

i.e.: change 'SYSFS' by 'ATTR'. Could you try?

I know that you know, but may be some newbie is reading this: do a backup before edit the files!

/etc/udev/rules.d/60-brother-brscan4-libsane-type1.rules
=============================================================
#
#   udev rules
#

ACTION!="add", GOTO="brother_mfp_end"
SUBSYSTEM=="usb", GOTO="brother_mfp_udev_1"
SUBSYSTEM!="usb_device", GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_1"
SYSFS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
ATTRS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_2"
ATTRS{bInterfaceClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceSubClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceProtocol}!="0ff", GOTO="brother_mfp_end"
#MODE="0666"
#GROUP="scanner"
ENV{libsane_matched}="yes"
#SYMLINK+="scanner-%k"
LABEL="brother_mfp_end"
--------------------------------------------------------------
/etc/udev/rules.d/60-brother-libsane-type1-inst.rules
=========================================================
#
#   udev rules sample for Brother MFP
#         version 1.0.2-0
#
#   Copyright (C) 2012-2017 Brother. Industries, Ltd.
#
#   copy to /etc/udev/rules.d or /lib/udev/rules.d
#

ACTION!="add", GOTO="brother_mfp_end"
SUBSYSTEM=="usb", GOTO="brother_mfp_udev_1"
SUBSYSTEM!="usb_device", GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_1"
SYSFS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
ATTRS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_2"
ATTRS{bInterfaceClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceSubClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceProtocol}!="0ff", GOTO="brother_mfp_end"
#MODE="0666"
#GROUP="scanner"
ENV{libsane_matched}="yes"
#SYMLINK+="scanner-%k"
LABEL="brother_mfp_end"

It must be mentioned that the Brother printers (5 x DCPJ525W) are all connected by Wifi, not via USB. The Beowulf machine serves the printers for that machines, which don't have drivers for the printers, e.g. computers with OpenBSD and NetBSD.
That works fine, independent from the error messages in the logfile.

Thanks for the recherche, Pedro.

Not really a recherche. I've spend my time in support Brother pages because I have a bunch of Brother devices.

Indeed. That is the very reason of buying again. Remember: "put your money where your mouth is".

Could you quote here these two offending files?

However Brother printers and scanners work perfect.

Does anybody know what my Brother scanner has to do with udev?

https://support.brother.com/g/b/faqend. … 100604_000
and search for udev...

Okay, so as it states in debian packages one could safely disregard xserver-xorg-video-intel if installed?

The Intel DDX driver is reportedly buggy but it does have advantages over the modesetting driver — xbacklight only works with xserver-xorg-video-intel, performance is (slightly) better and it offers a TearFree option to eliminate screen tearing (which can be a problem with Intel video cards), unlike the modesetting driver.

With Beowulf, boot time takes almost 3 minutes due to udev waiting and time out. This happens with kernel 5.6 from beowuf-backports. I've posted here:https://dev1galaxy.org/viewtopic.php?pid=22907
No clues why this is happening.

Got Beowulf on kernel 5.6 running fine on two desktop machines. You must have individual hickups, hardware problems or a device that having issues.

rolfie