When it comes to language support, GNU is really the only project that has bothered to properly support languages other than English; https://www.gnu.org/software/gettext/
LibreOffice is free software that utilizes the hunspell spell checking library, which currently has dictionaries in the following languages (the same dictionaries that aspell uses); Afrikaans,Bulgarian,Catalan,Czech,Welsh,Danish,German,Modern,English,Esperanto,Spanish,Estonian,Faroese,French,Irish,Galician,Hebrew,Croatian,Hungarian,Interlingua,Indonesian,Icelandic,Italian,Kazakh,Central,Kurdish,Lithuanian,Latvian,Maori,Macedonian,Malay,Norwegian,Dutch,Norwegian,Polish,Portuguese (Brazil and Portugal),Romanian,Russian,Slovak,Slovenian,Albanian,Swedish,Swahili,Tswana,Ukrainian,Zulu
As it's free software and the format encoding is free, you're free to add more dictionaries in whatever languages you want.
@keoni I'm curious as to the state of public word lists. For example, does Linux have a broader representation of languages that are available for open source use in tools like LibreOffice?
Everyone should know that spell check is broken in software you spend hundreds on because Microsoft insists you use a cloud service to check your spelling. This has broken custom spell check technologies indigenous people have built for their language.