SDDM does not unlock gnome keyring upon login

[lemmiwinks86]

I'm using Kubuntu, so I log in via SDDM (no auto login!). I also use Evolution, which always complains about the default keyring being locked after login or resume from suspend. Opening seahorse and checking shows that the default keyring is actually locked.
I have not made any modifications to /etc/pam.d/sddm and have all required packages installed (i.e libpam-gnome-keyring).

1)
Description: Ubuntu 20.04 LTS
Release: 20.04

2)
sddm:
  Installed: 0.18.1-1ubuntu2
  Candidate: 0.18.1-1ubuntu2
  Version table:
 *** 0.18.1-1ubuntu2 500
        500 http://de.archive.ubuntu.com/ubuntu focal/universe amd64 Packages
        100 /var/lib/dpkg/status

3)
SDDM should unlock default keyring from gnome-keyring on login

4)
SDDM does not unlock default keyring from gnome-keyring on login

[Launchpad Janitor (janitor)]

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