Where to begin to validate idea and find potential users? - Reddit

I'm a developer and I do have this idea which I want to validate by end users. The problem is that I actually don't know where to begin. One idea that came to me was launching an early signup app on app stores and circulate around. I probably don't need to build the MVP this way and use an signup app to validate if end users do exist for the product. I don't have better ideas, I don't want to ...