My setup works fine (sharing /tmp/.X.11-unix) with 0.8, but doesn't work with 0.9.
Depending what I've tried, I get various OpenGL related errors, and the GUI either doesn't show, or shows but isn't populated. In the state where it's show but not populated, if I click around I do get the correct dialogs appearing.
Some errors I've encountered ...
QOpenGLWidget: Failed to make context current
libGL error: failed to open drm device: Operation not permitted . libGL error: failed to load driver: i965