If your company’s contract allows it, you can create rooms with free access for all your colleagues. These are called “Public” rooms. This chat will be freely accessible to all the employees of your company with a Citadel Team account, wanting to exchange with you on the set theme.

Prerequisite: You need to be administrator or moderator of the room

In the thread :

Click on the cogwheel at the top right of your chat screen or click on the banner at the top of the screen (it displays the title)
The settings open on the right (by default this field shows the members in the room).
Under “Security”
Open the Section "Visibility : Private"
Choose "Public"

Your collaborators will then be able to find your room in the directory of public rooms.

Make a room accessible to all collaborators (Public)