I use the current LibreOffice extension LanguageTool 5.2.2 on both macOS Catalina and Ubuntu Budgie. I mainly create documents in the following languages: Dutch (Netherlands), German (Germany) and English (UK & USA).
Yesterday I noticed that the grammar check by the LanguageTool no longer works if the language of the respective document is set to Dutch. For documents with German or English language settings, on the other hand, the LanguageTool works perfectly. This error occurs under macOS as well as under Ubuntu.
Under macOS, this error is even more serious. The default language setting on my laptop with Ubuntu is German, the one on my iMac is Dutch. Therefore, when I want to create a new document in LibreOffice on my iMac, the language is automatically set to Dutch. However, with the default language set to Dutch, the LanguageTool does not even load properly. For example, if you want to call up the LanguageTool settings in the menu, LibreOffice hangs and then has to be stopped forcibly because the application no longer reacts. In addition, the entry for selecting the profile is missing in the menu. However, if I set the language of the document to German or English, the LanguageTool is loaded completely with all the menu entries and then works perfectly again.
With the update to the latest version, an error must have crept into the LanguageTool, at least with regard to the changes for the Dutch language.
Can you reproduce and confirm this error?