Comment 3 for bug 1816296

Using focal Kubuntu.
Firefox filling .xsession-errors
Has pyqt5 (5.14.1+dfsg-3build1) focal; & current versions of other dbus related files that are standard.

fred@z97-focal-kubuntu:~$ uname -a
Linux z97-focal-kubuntu 5.4.0-58-generic #64-Ubuntu SMP Wed Dec 9 08:16:25 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
fred@z97-focal-kubuntu:~$ echo $DESKTOP_SESSION
plasma
fred@z97-focal-kubuntu:~$ cat /etc/X11/default-display-manager
/usr/bin/sddm
fred@z97-focal-kubuntu:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04.1 LTS"
fred@z97-focal-kubuntu:~$ apt show firefox
Package: firefox
Version: 84.0+build3-0ubuntu0.20.04.1

** (/usr/lib/firefox/firefox:112432): WARNING **: 09:37:31.184: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112483): WARNING **: 09:37:31.636: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112515): WARNING **: 09:37:31.830: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112540): WARNING **: 09:37:31.970: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112609): WARNING **: 09:37:33.138: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112734): WARNING **: 09:38:27.515: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112782): WARNING **: 09:38:27.981: Unable to connect to dbus: Could not connect: Permission denied
** (/usr/lib/firefox/firefox:112833): WARNING **: 09:38:28.518: Unable to connect to dbus: Could not connect: Permission denied