Hi @Anonymous,
There is Yammer connection available under PowerApps.
We could add a gallery and set its items property to:
items = Yammer.GetAllMessages().messages

Which would show the messages in the gallery.
Currently there is no corresponding document talking about this.
You should be able to find the available functions about the Yammer connection thorugh
Yammer.

If you have any further questions regarding Yammer connection usage, please post back.
Regards,
Michael