I was about to put a theme for LO just for fun. I created a soft link to the (theme) file under
/usr/lib/libreoffice/share/config/
and
/usr/share/libreoffice/share/config/
I moved the sls and renamed them in there (using sudo).
LO was open but without any document. I went to Tools->Options-> and then to Themes or Skins or Appearance (don’t remember the name).
From the theme selection I chose one (it doesn’t matter because all was empty) and click OK instead of Cancel.
Now it won’t open after the splash screen.
My system is Ubuntu Mate and is up to date.
update: running it through terminal givs me the following (extract):
terminate called after throwing an instance of 'std::runtime_error'
what(): IconThemeInfo::FileNameToThemeId() called with invalid filename.
Fatal exception: Signal 6