Whatever interests you. the thing doesn't need to be commercial - what you learn by shipping might give you insights into problems to solve.
Of course the downside is you might be finding problems that only hobbyists have that wont make money. But you can do further validation to see if anyone will pay and if those problems extend to companies or solo professionals who will pay.
Of course the downside is you might be finding problems that only hobbyists have that wont make money. But you can do further validation to see if anyone will pay and if those problems extend to companies or solo professionals who will pay.