In Linux Mint 18.1 I have installed libreoffice-l10n-en-gb, but there is still no highlighting for misspelled words in Writer. In options language settings, locale setting is “Default - English UK”.
“Check for updates” is disabled under my “extension manager”, and there are no extensions listed.
Update
The spell checking is working for a “.doc” file I have but not for a “.odt” file that I have downloaded.