We know you are patiently waiting for this feature. This feature is being implemented in stages. Fast tenant switching is currently in testing both internally and with early customers. We expect to release to the public in the Fall. I’ll post an update once it’s rolling out.
Full multi-tenant, multi-user support will be added after fast tenant switching.
I agree I don't want fast switching. I want one instance of Teams to support multiple accounts within the same interface. I'm a consultant that has multiple Teams accounts from O365. I want it to function like Outlook where I can have multiple accounts connected and I'd get notifications from any of those from the one Teams app interface.