Adding an unsupported language to ODK Collect

1. What is the issue? Please be detailed.
I have a form that I have translated into English (en), Portuguese (pt), and Trió (tri).

The last language is not supported in ODK Collect, although it is in << >>. How can I add support for these less common languages? Can we add translations?

2. What steps can we take to reproduce this issue?

Try to change your ODK Collect language setting to Trió...

3. What have you tried to fix the issue?

I have looked at support forums, and tried different ODK collection apps (KoboCollect, Tella, ODK Collect). Do we need to translate all of the strings in ODK Collect to Trió through the Transifex service?

4. Upload any test forms or screenshots below.

A survey form can always be translated into whatever language you want - see the docs on form language. You can also set a default language for the survey to open in via the settings sheet of your XLSForm. When the form is open, click the 3 dots in the top right, select "Change Language", and pick the one you want. All of your questions and options will appear as translated in your XLSForm.

For the Collect app interface to appear in a particular language, it needs to be translated via Transifex and then included in an app release -