After I'v added "Text region utilities" it worked a little. But on next startups it begin to get into Plug-ins failed to strart" with the above plugin reported. And after I close the dialog and open "Tools -> Plugins... -> On-line gallery" system (Ubuntu Mate 16.04) hangs.
Also I couldn't reset SMath that the error stop appearing.

Thank you for reporting, I'll check if I can reproduce ASAP. The problem might be with the linking with WriterRegion.

However in the meanwhile you can go in ~/.config/SMath or in ~/.SMath (depending on your OS) and in extensions/plugins manually delete the folder a9f5e37d-83f5-4a4b-a106-0ba7b202abbb (text region utilities)

Wrote

Thank you for reporting, I'll check if I can reproduce ASAP. The problem might be with the linking with WriterRegion.

However in the meanwhile you can go in ~/.config/SMath or in ~/.SMath (depending on your OS) and in extensions/plugins manually delete the folder a9f5e37d-83f5-4a4b-a106-0ba7b202abbb (text region utilities)

I encountered the same problem. However in my case the folder "text region utilities" has a longer number:

a9f5e37d-83f5-4a4b-a106-0ba7b202abbb/0.3.6353.26919. The differences in Bold font.

Regards,
oftheair

Wrote

Wrote

Thank you for reporting, I'll check if I can reproduce ASAP. The problem might be with the linking with WriterRegion.

However in the meanwhile you can go in ~/.config/SMath or in ~/.SMath (depending on your OS) and in extensions/plugins manually delete the folder a9f5e37d-83f5-4a4b-a106-0ba7b202abbb (text region utilities)

I encountered the same problem. However in my case the folder "text region utilities" has a longer number:

a9f5e37d-83f5-4a4b-a106-0ba7b202abbb/0.3.6353.26919. The differences in Bold font.

Before I read the advice of Mr. Carpi I tried a lot of other measures, among others I have removed all plugins. Now it is a mess. Starting Smath results systematically in hanging of the system. I mean that the solution of this problem will be a complete removal followed by a reinstall of SMath. But how to remove SMath completely?

Regards,
oftheair

Wrote

in my case the folder "text region utilities" has a longer number:

a9f5e37d-83f5-4a4b-a106-0ba7b202abbb/0.3.6353.26919. The differences in Bold font.

0.3.6353.26919 is a sub-folder; in order to clean SS from the plugin you have to delete a9f5e37d-83f5-4a4b-a106-0ba7b202abbb and all his content

Wrote

I tried a lot of other measures, among others I have removed all plugins. Now it is a mess. Starting Smath results systematically in hanging of the system. I mean that the solution of this problem will be a complete removal followed by a reinstall of SMath. But how to remove SMath completely?

What plugins have you deleted? Those in the executable folder? These shouldn't be never touched; In this case simply download another smath studio package for Linux and delete the old one.
Full cleaning can be reached deleting all the content of the ~/.config/SMath directory (SMath folder and all his content; a new one will be created if you start again SMath Studio)

Wrote

But how to remove SMath completely?

No procedure has been reported, from recollection.
Similarly to evaporate Mathcad and in order:
1. Add/Remove program ... delete Smath
2. From the Program File directory ... delete Smath
3. from regedit.exe ... delete all Smath entries from any/all registries
4. I have no proof it evaporates Smath completely.
=================================================
Re-download Smath. Install but before installing, better download
all the plugins, then install, then activate from the gallery menu.
You should have a bran new Smath of the version you just have downloaded.

The "evaporate procedure", install new is dramatically missing
from the main web page about Smath.