Hmm well the Control (or option) click as an alternate seems to work quite well but it will only send a SINGLE right-click. If your application on the SUT has a context menu that requires the right mouse button to be held down then this is going to be a problem.
Unfortunately there isn’t much we can do to Vine Viewer in the short term to resolve that issue. There might be a utility for Linux running on Mac’s that would help with this situation.