“Go find a niche one where people are gonna find it valuable enough to spend money and then two where there is some form where you understand how you're going to get attention for it.”

Two Filters for a Viable Solo App Niche: Pays Money + Has Built-In Attention

The two-filter test for evaluating an indie app niche: first, do people in this community already pay for things they value? Second, is there an existing channel or community through which you can reach them without paid advertising? Both filters must pass. A passionate community that does not pay is a content project. A paying audience with no accessible channel is a distribution puzzle you may never solve.