Hi Florian!
Thanks for reaching out to us! Let me help you with that.
By default, email alerts are only sent to the email addresses you specify in the “Email addresses to be notified” field (just like in the screenshot you sent). If you want to send an email notification to the users, then you can do so, but will involve some custom coding.
This does not work and no mails are sent to the creation of an event
If your settings are like in the screenshot and no email alerts are sent to the email address when an event is submitted via the community form, then this is an issue.
I tried it in my own installation and seems to be working fine, so this could be a theme or plugin conflict. I see you already tried deactivating all other plugins, so you should now try switching to a default theme like twentyseventeen and see if the emails are sent.
If not, then we’ll need to make some deeper troubleshooting.
Let me know how that goes and if you have other questions.
Thanks,
Victor