It would be really nice if it there was a UI where you can disable Akonadi on computers where it's not in use. Because being in use or not, it always seem to start a large mysql process (around 130MB of RAM). In KDE4 there was an module called akonadiserverconfig (or something like that) where if you knew it you could set it to use a non-existing seperate database server. This effectively disabled the process. Reproducible: Always
Is this configuration not available in the current version of akonadiconsole? - it was in KDE4. menu bar - Server - Configure Server...
I installed akonadiconsole (not installed by default) and it comes with a pretty hefty warning upon opening: "Akonadi Console is purely a development tool. It allows you to view and change internal data structures of Akonadi. You should only change data in here if you know what you are doing, otherwise you risk damaging or losing your personal information management data. Use at your own risk!" When started: the menu bar -> server -> [does not contain configure server. Only start/stop/restart server] I don't think this option matches "A nice UI" :-)
Indeed the KCM to configure Akonadi is gone in KF5. However Akonadi is started on demand, which means you must be using some application that requires Akonadi. One of the candidates might be KOrgac or KAlarm, which runs in the background, but you can open them via systray and turn them off completely (disable autostart on login). I'll close this as WONTFIX, since we have the on-demand start behavior, so there's no need for an UI.
So it's a default setup issue, Kubuntu should not enable KOrganizer (which I can confirm lies hidden in my systray) by default unless they want to equip the user with an Akonadi and mysql server, right ? I can not detect kAlarm running on my system.