I think Hashimoto has the right idea with Ghostty. If you have the financial / time freedom (and the spousal support) to tinker with a passion project, that seems like a great way to spend your time and skills without commercial pressures contributing to burnout.

I always like Neal Stephenson’s approach with his Sci-Fi novels too. Most of them have a central conceit based around a topic he wanted to learn more about (linguistics, nanotech, cryptography, etc…), so in essence writing the novel was just an excuse to obsess about that topic for a while.