What is a niche hobby of yours that you are fascinated by and would like to share with others?
I'll start. I have recently gotten into 3D printing, and, while incredibly frustrating sometimes, there's nothing more rewarding than getting a perfect print.
Csound coding. Most musicians are thoroughly ensconced in their relatively-easy-to-use hardware and software. Me? I want to have sample level control over everything by writing reams of code and come up with algorithms that generate interesting textures, melodies, harmonies, and rhythms.
I release almost everything I write through Distrokid as "Underwaterbob". So, it's all on whatever they release to, which is all the usual suspects like YouTube, Apple Music, and Spotify. Here's the YouTube channel. The most Csound heavy recent releases are "Abiotic" and "Voltaic Fauna Bodies" though on the latter I use hardware synthesizers driven with MIDI files I generated in Csound. Sometimes physical knobs are nice.