How do you turn build-in-public social traffic into actual app signups?

I gave the open building strategy a honest try for my last project. I posted progress milestones almost every day but while the engagement was decent the conversion to real users was basically zero.

It makes me wonder if people just like watching the journey without ever needing the actual software.

For those who actually got traction this way what specific type of post or update actually made people click through and try the product?