User switching does not work: my_switch_to_username: assertion 'p->dm_seat != NULL' failed

[Erik Meitner]

Actual behavior:
Switching users from the indicator menu does nothing. Only this is logged in /var/log/syslog:
Jul 17 23:11:01 cherna indicator-sessi[5227]: my_switch_to_username: assertion 'p->dm_seat != NULL' failed

Expected behavior upon selecting another user in the indicator menu:
Switches to a screen with a A password prompt.

Ubuntu 20.04.2 LTS
indicator-session 17.3.20+19.10.20190921-0ubuntu1

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: indicator-session 17.3.20+19.10.20190921-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-77.86-generic 5.4.119
Uname: Linux 5.4.0-77-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.18
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: Unity:Unity7:ubuntu
Date: Sat Jul 17 23:34:43 2021
EcryptfsInUse: Yes
InstallationDate: Installed on 2013-07-29 (2910 days ago)
InstallationMedia: Ubuntu 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130213)
SourcePackage: indicator-session
UpgradeStatus: Upgraded to focal on 2021-07-10 (7 days ago)

[Erik Meitner (e.meitner)]

My default desktop was set to "Unity"(at the login screen). I changed it to "Ubuntu" and logged in. Now user switching works.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.