I would like to implement the following Scenario: Within a Meeting that should take place in the real world in a room (not necessarily within MS Teams), I want a Microsoft Azure Chat bot to post a message to the meeting-chat, without someone having to add the bot to that meeting chat.
I noticed, that real proactive messaging to MS Teams is still not possible, a workaround is necessary: Catching a conversation reference including the users teams-chat-id while he adds the bot e.g. via personal teams app. This works good, if the teams app is pushed to all users within an organization via policies.
This workaround however is not possible within a meeting-chat, that might not exist at the time the bot should write to it. So, no possibility to catch a conversation reference to post to.
Also, I noticed that there does not even exist a MS Graph endpoint neither a connector within Logic apps to post a teams message to several users without cannel-context.
Do you see any workaround for this scenario, or is it simply not supported?
To my knowledge, you're right on both accounts - a bot can't proactively message a chat that it's not part of, and I don't think Graph supports messaging to group chats altogether, which is your scenario.
Just on a point of correctness though, a bot can proactively message (a) individual users (1-1), (b) group chats, and (c) Team channels, each separately (i.e. it does not need to be installed by each user, and message each user privately, unless that is the desired scenario. All that's required for each of these is the relevant "conversationid" that represents the specific conversation, and the ServiceUrl.