On DistroKid's upload form, there's a list of languages. The list contains all of the languages that are officially supported by streaming services.
If your language isn't listed, it's best to select "English" and write your song & album titles in the Romanized form of your language.
Then later, if your language ever becomes officially supported by services, you can remove & re-upload your album if you like, in your local alphabet.
It should be noted that we are not able to distribute Cyrillic titles/Slavic languages or Chinese content to iTunes at this time, and we do not foresee being able to do so in the near future.