Sometimes it's hard: for many kinds of projects, I don't think anyone would use them if they were not open source (or at least source-available). Just like I wouldn't use a proprietary password manager, and I wouldn't use WhatsApp if I had a choice. Rather I use Signal because it's open source.

How to get people to use your app if it's not open source, and therefore not free?

For some projects, it feels better to have some people use it even if you did it for free than to just not do it at all (or do it and keep it in a drawer), right?

I am wondering, I haven't found a solution. Until now I've been open sourcing stuff, and overall I think it has maybe brought more frustration, but on the other hand maybe it has some value as my "portfolio" (though that's not clear).