Here's how to add a language to a project in Weblate:-
Log in to Weblate: Make sure you're logged into your Weblate instance with the necessary permissions (Administrator or Maintainer).
Pick one project - Kodi Core would be logical, Pick one component in Kodi Core - Kodi main would be logical →
https://kodi.weblate.cloud/projects/kodi-core/
To the right of Kodi main there is a square box, see image. Click on the square box:-
https://i.imgur.com/ftD7H5E.png
https://i.imgur.com/MjdahSd.png
If you have enough permissions, you should see a list of languages on the next screen. Click on the plus arrow, see image
https://i.imgur.com/TtNjzjE.png
Now fill in the language, Irish, or Gaeilge, see image showing French added:-
https://i.imgur.com/2MoiRN4.png
Click on 'Start new translation'
If the Language Is Not Available (how the language is listed already
https://kodi.weblate.cloud/languages/ga/) :-
If the language is not listed in the dropdown, you'll need to add it to Weblate's supported languages:
Edit languages.json:
On the Weblate server, locate the languages.json file. It is usually in the /app/data/ directory (or similar, depending on your installation).
Add an entry for your language using the correct ISO 639-1 or 639-3 code. Example:
{ "code": "ga", "name": "Irish", "plural": "(n != 1)" }
Restart Weblate: After making changes to the languages.json file, restart the Weblate service for the changes to take effect:
sudo systemctl restart weblate