“alternate shell” doesn’t seem to work anymore in recent versions of Windows, RemoteApp is the way to go.
remoteapplicationmode:i:1
remoteapplicationname:s:Purpose of the app shown to user...
remoteapplicationprogram:s:C:\...\some.exe
remoteapplicationcmdline:s:
To get this to work under e.g. Windows 10 Professional, one needs to enable some policy:
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services]
"fAllowUnlistedRemotePrograms"=dword:00000001