the LanguageTool for LibreOffice/OpenOffice didn't check the spelling mistakes. As you see in the first image i have installed both the LanguageTool and Hunspell. Hunspell is correct recognized as spelling tool. The LanguageTool is only recognized as grammar tool, but not as spelling tool, too. You can't select any language dictionary because LanguageTool is only recognized as grammar tool.
I have Java 1.8.0_141, LibreOffice 188.8.131.52 and LanguageTool 3.8.