First of all, you don't want to spend tonnes of tonnes of time "researching". In fact, 99% of your "researching" is actually just procrastination. This post will give you everything you need to pick your niche; you don't need to read countless articles, you need to start taking action.
If you dive into a niche and then after a couple months realise that there's a better one out there for you, then that's fine - you'll be able to PIVOT to a new niche and bring all the skills that you learnt in your old niche with you.
The very first niche I entered was "Stoicism"... Yup, I talked about ancient philosophy. Unsurprisingly, that wasn't the best niche for me and I've now pivoted into the "helping people become fulfilled by creating profitable online businesses" niche. But what I'm trying to say is: I would never have found this new niche if I hadn't got started.
Now, on the other camp is the people that don't do any research and just dive in and start "following your passion". That is bad advice. Following your passion is 1/3 of the equation, and if you ignore the other two you are destined to fail.