When trying to install the Teams system-wide on an RDS, you might get this error stating that no VDI environment was detected:

msiexec /i "Teams_windows_x64.msi" ALLUSER=1

This is because the installer checks if these registry entries are present on the system (Citrix or VMware):

HKLM\Software\Citrix\PortICA DWORD ALLUSER 1

So the solution is easy: just manually add the Citrix key you are good to go. Teams should work just fine on a RDS that is not provisioned by Citrix or VMware Horizon (why shouldn't it?).