Hello @cirrus7, and thanks for your feedback (and attached samples) !
Concerning your uploads:
The Error 13 indeed happens because the Scene is empty. Except if there is something I don’t understand here, I think that this is the expected behaviour, as there would be no point to display a non-existing model on Sketchfab.
That one was indeed a little bit more tricky. We did not take into account the possibility of objects disabled in the viewport in the first version of our support for Blender 2.8, which caused crashes.
A fix is going to be deployed soon to fix this error.
Exporting parts of the scenes only
Concerning hidden objects and “render helpers”, it is true that the behaviour is not always the most intuitive…
We usually “un-hide” those and export them to Sketchfab as such objects are often used as particles, boolean parts, curves… and often needed for the final models to look good.
Although we’ll try to make this more intuitive when processing the files on Sketchfab, one suitable option you could use would be to use the Sketchfab add-on if you have not tried it yet !
It has an export feature with a “Selection Only” option, which should allow you to export… only the selected objects
You can download it on github (I’d suggest installing the latest version, the 1.2.1): https://github.com/sketchfab/blender-plugin/releases
Thanks again for your feedback, let me know if something was not clear or if I can help further !