I read about digital gardening / digital puttering[0] several years back and that resinated with me a bit. I don't necessarily need major projects in my free time; that would feel like a burden on top of my job. What I do instead is have some relatively simple stuff I can putter around with. Add a feature here, refactor some code there, etc. It's not going to change the world, but they are things I find useful or interesting, even if they aren't a big deal.
I ran across an interview[1] with James Thomson (developer of PCalc) a while back. If I remember it correctly, it seems like PCalc started out like, and still serves as his digital garden, even though he does make money off it. He needed a project to learn on, so picked the humble calculator as the idea. Then just kept going. Any time Apple released a new technology, he'd use PCalc as his test bed to learn it. Even when he wanted to learn 3D graphics, he ended up making an About screen for PCalc (as it's own app), that was basically a little 3D playground (a bit like the easter egg from Excel 97[2], but with more).
That would be my advice. If you just have a few hours here and there, and are already making an impact at through work, don't let the FOMO eat you up, just tend to your garden. Maybe it will turn into something others will use, maybe not, but don't stress about making that a goal.
[0] https://maggieappleton.com/garden-history