Problem

For tasks, having generic 'en' as target language, 'en-GB' is used for SpellCheck instead of generic 'en', despite generic 'en' is supported by LanguageTool.

Solution

Logic for detection of whether task's target language is supported by LanguageTool - must be improved to handle cases described above, so falling back to sublanguage should happen only when main language is not directly supported by LanguageTool