As this problem did not occur on a freshly-created user on the same system, I deduced that this problem was most likely due to an old configuration setting which is not (no longer) properly supported.
Removing Akonadi's settings (directories) inside ~/.config/ and ~/.local/share "fixed" seems to fix this problem.
As this problem did not occur on a freshly-created user on the same system, I deduced that this problem was most likely due to an old configuration setting which is not (no longer) properly supported.
Removing Akonadi's settings (directories) inside ~/.config/ and ~/.local/share "fixed" seems to fix this problem.