Teams will always log into the domain-joined PC account
If a user has two different Microsoft Teams accounts and has a domain-joined machine, Teams uses the domain-joined profile on the machine to automatically log the user into Teams.
To switch to the other Teams account, the user must manually log out of the app and enter credentials to the second account to log in. If the user logs out of Teams and restarts the machine, upon restart, Teams will automatically log in using the domain-joined profile.
If users are signed in to a domain-joined computer and don't want their user name pre-populated on the Teams sign-in screen, admins can set the following Windows registry to turn off pre-population of the user name:
(UPN) Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\Teams SkipUpnPrefill(REG_DWORD) 0x00000001 (1).
Skipping the user name pre-fill for user names that end in ".local" or ".corp" is activated by default, so a registry key does not need to be set to turn these off. For more information, see Sign in to Microsoft Teams using modern authentication.
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