On Windows for some reason libreoffice has spell checks working just fine but on Linux it doesn’t work at all. I believe this may have to do with missing extensions but then how come on Windows it exists but not on Linux?
Anyways I am looking for English Australian spell checks, anything I can do to get it working?
Install hunspell and hunspell-en_au.
A tip for the future, you can see the list of optional dependencies for any installed package by passing the -Qi option to pacman. 
EDIT: fixed the typo, sorry about that 
unfortunately hunspell-au doesn’t even exist in the AUR 
Cool mate, so like do I type pacman -Qi libreoffice-fresh?
I had similar problem recently. If you download the relevant language pack for Libreoffice, this doesn’t enable the spellcheck function. Try downloading the relevant Australian English dictionary from:
https://extensions.libreoffice.org/en/extensions/show/english-dictionaries
In Libreoffice menu open Tools/Extension manager, select the downloaded file, then restart Libreoffice
Sorry, it’s hunspell-en_au, it’s in the repos.
Thanks but I think @Kresimir suggested easily using terminal
Precisely… and there you see that is uses hunspell for spell checking. And then you can look up language packages for hunspell:
pacman -Ss hunspell
Thanks bro
That;s how I got mine to work.