I think the secret of Reddit is to interact in an authentic, humble way (Sorry I don't find other words to describe this) on targeted subs. For me, what worked, is to share the app on /r/electronjs because it was made with Electron: "I published my first app built with Electron, love the framework. Let me know what you think!" Or on /r/api: "I created a mock API tool, my first big side project. I hope it can be useful for some people."

And the more you interact and ask for feedback the better it is.