Browser Profiles
Chrome supports multiple profiles, they just open in new windows rather than different tabs. Works a treat for keeping all the different O365 accounts separate (and that increasingly includes for voluntary groups as well as work clients)
The frustration with the Teams client for Windows however is quite justified... Outlook is sitting there quite happily supporting six different Office 365 accounts simultaneously, letting me receive emails from any of them and send with little more fuss than a dropdown to select the account. Teams on the other hand is struggling with my work account and one client 'guest' profile; to support any more requires major logging out and and in again. Ironically the best client I've found for Teams so far is on the iPad...