Windows 10 on Acer Aspire Switch 10 (essentially a tablet) - I added a few dictionaries ( Hebrew, Arabic, English, French) Could that be the reason?
Thanks,
MaxineKL
Open your file browser (Windows Explorer as opposed to Internet Explorer), select the Program Files or Program Files (x86) folder, open the LibreOffice folder, open Share, then Extensions, check the size of the dictionary folders. For English, that’s 34 MB on my Win 10 system. Overall size of Libre is near 400 MB, for OpenOffice some 350 MB.
If this answer helped you, please vote it with 
(here on the left). That will help other people with the same question.