After failing to start Akonadi with MySQL on my new Ubuntu installation, I found a tip to try Postgres.
After setting up the Postgres server, user and database, adjusting the Akonadi configuration to switch to Postgres things still wouldn't work.
Through trial and error I found that I was missing some packages:
sudo apt-get install akonadi-server akonadi-backend-postgresql
Changing the configuration file was inspired by the article Setting up Akonadi where most of the options for Postgres were empty:
The winning combination seems to have been empty
InitDbPath, and the correct
Name (I had to add my username after akonadi).
After starting Akonadi service:
$ akonadictl start
The configuration now reads:
After that Akonadi started and the service reported running (
Starting KOrganizer after that worked without any Errors saying Akonadi wasn't running. I was able to import my old data, tweak the configuration (I had to recreate the Categories), and creating new events and tasks works without issues.