@AndreyRuban I just got:
Circling back on this, I ran msiexec /i mattermost-desktop-5.9.0-win-x64.msi ALLUSERS=1 APPLICATIONFOLDER='C:\test\mattermost' and everything ran as expected, I now have a per-machine installation at the specified folder.
I do see a slight different in characters in the command provided by the user (‘ instead of '). That could be the issue? Otherwise, do we know if the customer is using a distribution environment like SCCM?