Does anyone have any advice on building in public while protecting your IP?

Work fast, stay ahead of someone who would steal it. Most likely, if someone is going to steal it, they aren't going to be successful. They are looking for a quick hit but no business is that.

let me tell you the truth, no one literally no one cares about your idea, go build in public

Your app idea is presumably solving a problem that exists. Which means other people know about that problem and have their own solution. What makes your app unique is how you approach the problem and how you implement the solution. If you browse through the last few weeks of launches, you'll see multiple apps that are doing the same thing in different ways. Even if someone did steal your idea, their app would be different than yours. But it's really not an issue. Building an app takes a lot of effort and enthusiasm - people get much more excited about working on their own ideas than other people's ideas.