If the setting “Availability: Internal only” is enabled, only internal users can interact with the Broadcast ID in question, i.e., subscribe to feeds and use bots. Internal users are the ones who are present in a distribution list or group.
Availability: Internal only is enabled by default and can be changed in “ID configuration > Availability”.
If Threema Broadcast is used in conjunction with Threema Work, the distribution list “All” gets populated with all contacts of the corresponding Threema Work subscription.