I'm a newbie to React development. I have read that the manifest.json file contains information about a Web App, and it may be useful in some cases. What am asking, though, is if it's safe to delete it.
For information about what the manifest is for, this answer may help you but to answer your question:
Yes, you should be completely fine deleting the manifest.json as well as <link rel="manifest" href="%PUBLIC_URL%/manifest.json" /> in public/index.html, so long as you're fine with losing the benefits it provides linked above.