Nick, I am also a consultant and setup as a Guest on a dozen different client/tenants. More and more I am seeing real-time notifications pop-up from all tenants regardless which tenant I am currently using. (I am logged into Teams on several PC's in the office; all are acting the same way.) Teams on my phone (Android/Pixel) is also notifying me from the different tenants. Hopefully you will also start seeing this behavior.
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