Short answer
The only way to “force” the files in a folder to be the owner of the owner of the folder is that other users have access only to it.
Explanation
If users can add files to a folder, there is no way to avoid that they add files belonging to another user and then to the folder owner.
Bypass
Instead of allowing users to directly add files to folders, implement another way to add files to this folder. There are several alternatives:
Use Google Forms. Google recently added a upload file to Google Forms. It is available only to G Suite users. Link: Change form , article from Google Docs help
- Google Apps Script.
- .
API Google