I’ve noticed there is no option to limit the app ‘talk’ to certain groups (as is the case with certain apps like monitoring. How can I achieve this without this option please?
The user list is not pulled from the contacts app, but from the sharing app.
You can use the feature to limit sharing to users in the same groups,
this setting is respected by the app. You can find it in:
Settings > Admin > Sharing >Restrict users to only share with users in their groups