Channel with all users? (Like Town Square)

Is there a way to create new channels like Town Square or Off-Topic where all users (also new users) are automatically added to?

Hello @GOhrner!
Have you taken a look at the Mattermost Welcome Bot ?

On the GitHub page (linked above), it is described as:

Use this plugin to improve onboarding and HR processes. 
It adds a Welcome Bot that helps add new team members to channels.

I can speak from experience in using this bot in my own Mattermost Instance that it is quite helpful!