Sure if all you have is a string you can use
textContent, but you still need to not overwrite it.
For this project, I’m not sure how bad it is to leak the ID. And technically you can just pass the tests and then delete the ID. Otherwise, you would have to find some solution. Like for example setting up your own backend API to proxy the requests (here is a video you can check out with an example of this).
If you just want some practice with using APIs and doing some light DOM manipulation using that API data you can find a bunch of free APIs to use.
But if you want to do this assignment I would suggest approaching it like a larger app possibly with both front and back ends and using the real Twitch API. As said, with a backend you can have it handle the API requests and your client will fetch the data through your backend. It is a lot more work but will also teach you some important stuff.
Remember this is just a pretend “take-home” assignment for you to get more practice.