Comment 21 for bug 1798091

I'm running MATE 18.04.4 and have this problem.
The fix above needs to be tweaked slightly for my system and I just wanted to note how. Basically, the tmp file names can vary between Ubuntu flavors and to get the right one you need to consult your /var/log/syslog file. Here's a snippet from mine.

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Mar 24 12:55:01 HOST kernel: [168408.433315] audit: type=1400 audit(1585068901.826:56): apparmor="DENIED" operation="open" profile="/usr/bin/evince-thumbnailer" name="/tmp/.mate_desktop_thumbnail.8S5NH0" pid=18303 comm="evince-thumbnai" requested_mask="wc" denied_mask="wc" fsuid=1000 ouid=1000
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The 'name=' entry tells me I need to add the following line to my
    /etc/apparmor.d/local/usr.bin.evince
file
owner /tmp/{,.}mate_desktop_thumbnail.* w,