Ask HN: Can a small free time project make a profit?

There are days when I have free time during my work. I use this time to study new technologies and create small free-time projects, just for fun. For example, I have developed my own smart-home automation, some test web applications, a few programs in Rust, C#, Python... I am learning and trying something new to improve my experience. So I was wondering if I could make some money on it. I don't mean to strongly commit my free time to another employer, but just to develop something in my free time. I am interested if you have experience with this, if you have tried something similar. If you have any tips, ideas, stories, I would be very happy to hear them.