Just to avoid issues and lost of time to other Matomo users.
The premium add-in “Media Analytics” is not compatible with SharePoint Online, due Stream on SharePoint has an embedded media player that Matomo doesn’t detect.
So don’t even try it.
According to the documentation for Stream here: https://learn.microsoft.com/en-us/stream/portal-embed-video
It looks as though the Stream video is embedded as an iFrame, so it wouldn’t be possible for Matomo to detect it as a Video player or track any actions taken in the player because of the security of an iFrame (A parent page by default cannot access any content of an iFrame unless the iFramed page specifically breaks its own sandboxing)