@dissolvedpet said:
Language not available
I'm trying to add a First Nations language to an Australian film which is entirely in two indigenous languages.
It's not one of the options and it's not letting me add the language.
How can a language be added?
I've tried searching for an answer but I can't figure out a specific search to address the issue of adding a language to the database, rather than just adding a pre-existing language option.
Thank you in advance!

language-COUNTRY
I believe that the language/Country you want or suggest is not part of the ISO 639-1/ISO 3166-1 list.
Therefore, it is still not possible to fulfill your request.

A migration to ISO 639-3 is on the Trello To-Do list.
https://trello.com/c/nVWNmwa7/245-migrate-to-iso-639-3
Migrating the entire system from ISO 639-1 to ISO 639-2 or ISO 639-3 is a huge job.
See here an explanation from admin Travis Bell.
https://www.themoviedb.org/talk/65278016fd63005d798fb419#65305b68a6a4c100ca4ab372

See below how TMDb manages languages and countries.
TMDb uses ISO standards to identify Languages and Countries.
ISO 639-1 alpha 2 for Languages. Standard with 184 Languages.
This standard assigns 2 lowercase letters for each language.
https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
ISO 3166-1 alpha 2 for Countries. Standard with 239 Countries
This standard assigns 2 capital letters for each country.
https://en.wikipedia.org/wiki/ISO_3166-1
Example:

en-US = english-United States  
fr-CA = french-Canada  
pt-BR = portuguese-Brazil  
hi-IN = hindi-India  
zh-CN = chinese-China  

And there is a list of language-countries supported by TMDb.
If you have an API Key you can make an API request to get these lists.
get/configuration/primary_translations
https://developers.themoviedb.org/3/configuration/get-primary-translations
https://api.themoviedb.org/3/configuration/primary_translations?api_key=THE_KEY
get/configuration/languages
https://developers.themoviedb.org/3/configuration/get-languages
https://api.themoviedb.org/3/configuration/languages?api_key=THE_KEY
get/configuration/countries
https://developers.themoviedb.org/3/configuration/get-countries
https://api.themoviedb.org/3/configuration/countries?api_key=THE_KEY