Hi @SteveTaylor ,
Unfortuneately, like you say, the notifications dosen't work when being send to a team or group.
But, this should be a good work around. Use Office 365 groups to find the group members for your group/team and use the same input as have in your message that you post in the team, in a post a feed notification.
When you add the post a feed notification and add the 'UserID' in userId the flow will automatically make an apply to each, which will then send out the notification to everyone in the team.

Right now, as far as I know, this is the easiest/best workaround to do this.
Let me know how it goes 😄
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Best Regards
Heartholme