I am now living that dream. When I left my last company, in 2017, I looked at working for someone else, but was almost immediately told that no one wants old men. It was pretty crushing.
But I went and set up a corporation that allows me to get equipment and testing kit, and started to write my own stuff. I explored surveillance cameras and ONVIF, as well as Bluetooth (I'm pretty good with devices -I've been working on them all my life. I started as an EE, and actually played with Heathkits when I was a kid).
I'm now working on a very ambitious social media app. It's probably months down the road, but it will happen. I always ship. I've been doing it all my adult life. This project is the kind and scope that is usually done by a team of 10-20 engineers (I also wrote the backend from scratch, three years ago), but I've been doing it alone. I just started working with another guy that will be adding a dashboard to the server.
If you look at the projects in my portfolio, you will see heavy-duty, industrial-strength code; not sloppy "hobby" code. The code Quality is out of this world, they all have a lot more testing code than implementation code, and the documentation is over-the-top complete.
I learned, long ago, to make my "hobbies" "ship" projects. That way, everything I do is useful.
And that is what makes me happy. I like to finish stuff; and having people use my stuff is the best way to validate its completeness.
That said; despite the completeness of my work, it isn't particularly popular, which is just fine by me. I tend to "eat my own dog food," and use a lot of my libraries in my own work. The less that people other than myself depend on my work, the more freedom I have to form it to my own needs. I take Stewardship of my work seriously.