How to localize S-app (someone’s Qt app)?

1. You need to find .ts localization file. Usually it’s separate file for every language in the languages folder in the S-app source repository.
   Examples:
   lang_en.ts-— source English localization file
   lang_en.qm — compiled English localization file (used by working app)

2. .ts file is XML, so you can modify it as plain text, but more convenient is using Qt Linguist. It is included in Qt framework, but you can download it as separate app for Windows here (unofficial).

3. Copy English.ts, rename to your_language.ts, change the language tag in the begining of the file manually using a notepad.

   <TS version="2.1" language="en_US">
   

4. Open both file in the Qt linguist, and make a translation.
5. Save your_language.ts file
6. You can test your translation: using Qt Linguist, compile your_language.ts to your_language.qm, and test it with app package (put to S-app language/ folder)
7. Send your_language.ts to S-app author.

More info here