Afaik the only really viable hydro farms right now make greens like kale, lettuce, basil etc, and in places where the climate or space isn’t suitable for farming them outdoors.
Almost all vegetables in my country are domestic greenhouse farmed with additional light and gas heating (they run big gas generators that provide both electricity and heat), a lot of them are for export too. But we have expensive land, cold weather and cheap natural gas.
You could also do flowers like orchids and tulips. Not hydroponically but easier to start off small scale (because they’re more expensive).
Microgreens are becoming more popular, are very easy with very low investment, but maybe it’s a hype that will blow over. Also there is a huge shortage of hops in pretty much the entire world so you could look at those too, many indoor hop growing start-ups seem to have survived their first 5 years. I’d probably start with a small setup with either herbs or microgreens. The good part about herbs is that you can dry them for longer shelf life while you look for a buyer.
Don’t go into chillies, they take long, are very niche and very cheaply grown abroad