Send Activity Notification with Application permission doesn't support Multi-Tenancy

ssj_springctin -
It is not explicitly stated whether the Send Activity Notification with Application permission supports Multi-Tenancy. However, it is mentioned that the activity feed notification API doesn't support cross-tenant notifications for apps in a shared channel. This suggests that there may be limitations with multi-tenancy in certain scenarios.

Basically when you request an application token, you need to request it for the tenant of users you want to send notifications to.

Doing so requires that an admin accept your app consent for each tenant. More information can be found here:
https://learn.microsoft.com/en-us/graph/auth-v2-service