My 2 cents for non-nextGen connectors:
QGIS → Viewer issue with non-selectable features in the viewer is due to the old version of QGIS connector it was sent from: it is solved in 2.20.1-alpha and following versions
QGIS → Rhino (v2 & NextGen) and ArcGIS NextGen → Rhino v2 are not the target workflows, the goal is to clean up outdated features in nexGen (which means some of the features sent from v2 connectors will not be supported, and vice versa)
Finally, v2 to v2 (QGIS to Rhino) colors issue from here I will check again 