It does work with KSP 1.9.1.2788 (Linux Steam Version, Infernal Robotics - Next v3.0.0, installed via CKAN 1.27.2).
It didn't work directly, I've reinstalled it via CKAN and clicked around in the Toolbar-Controler Settings (where you can configure to use a 3rd-Party or Stock-Toolbar or both, although i haven't installed any third party toolbars).
Now I can open the window via the Stock Toolbar.
But I've seen glitches like two robot arms controlled together (moving parallel away from the ship) seemed top turn into different directions, where one clipped into the ship. After Save & Reloading both arms appeared where they should be.