Until ParaView MR 5283, plugins that want functions invoked upon load were required to use the pqAutoStartInterface which (as you can infer from the class name) requires Qt. Recently, Paraview got more careful about loading plugins in python scripts when no GUI was present, meaning that this method would leave pvpython scripts with no way to ensure a plugin was properly initialized.
For SMTK, this meant that Manager instances were never passed to Registrar classes when running pvpython – so resource types, operations, views, etc. were not made available.
In the next few days, the ParaView MR and a matching SMTK MR will be merged and offline python scripting with SMTK will start working again.