If you would like for Teams to be installed but to not launch without user intervention there are a few things you can do to accomplish this.
First you will need to go here and download the adm and adml files for the GPO. Once you have downloaded them and the .exe has completed you will need to copy the admx file to C:\Windows\PolicyDefinitions then while there copy the .adml file over to C:\Windows\PolicyDefinitions\en-US.
Once you have completed that you can now go to your Group Policy Management Editor. In my lab I just added this to the Default Domain Policy under user configuration –> Policies –> Admin Templates –Microsoft Teams and enabled “Prevent Microsoft Teams from starting Automatically after installation”
That takes care of the GPO settings. Now if you or your users have already launched Teams then you also have to run this script There are a few things to note on the script. First if you do not want Teams to launch at all you need to edit the line $desktopConfigFile.appPreferenceSettings.openAtLogin = $True to $false. Then run the script, possibly run gpupdate /force on the desktop or wait until the policy pushes out and reboot. At this point you should not see Teams launch at all.
Should you still want Teams to launch but not sign in you can take that same line and flip it to $true. This line is simply changing the settings in the .json file found in %appdata%\roaming\Microsoft\Teams file is desktop-config.json The line is
Now once this is all set and working your end user if they prefer can go to settings and check “auto-start application” if they would rather have the app auto start.