"Underserved?"
Finding a niche that doesn't currently have a good product/market fit is an exploratory exercise.
For text based, many are using twitter to drive traffic to substacks, it's the go-to for analytics of what's trending, who's who and the small windows of opportunity that rises from time to time.
Developing your voice and a willing audience that finds enough value in it to fork over cash, you'd have to start at the basics.