What about functional thunar plugin for Insync3? All updates (even last two 3.0.24 and 3.0.25) completely ignore the fact, that thunar plugin still (from the first release of Insync3) does not work at all!!!
I think that is really the time to renew as soon as possible the support of the thunar file manager integration with Insync3. Your promises announced here, regarding active developing of thunar plugin, are endless but they are still remains only as promises … any useful thunar plugin is still not available. This is a shame!!!
Moreover: Removing the command-line (headless) interface for Insync3 seems to be a major mistake in the light of current experience. For many types of tasks, the ability to use CLI is crucial (routine tasks managed by appropriate scripts). In addition, your evidently poor assessment of providing users with only interactive GUIs is degraded by the lack of reliable and functional integration with some file managers (Thunar, for example). So I strongly recommend a fundamental review of the overall Insync3 concept.