Various degrees of niche-ness:

• modern boardgames. I've been fascinate by them since before I could write. I would draw my own roll and move boards and my mom would write down my instructions of what space would do what. From there it only grew and now I have more games I can play.
• rpgs. The most recent addition. I had always dismissed them as a potential hobby because it was advertised to me with videos of actors basically doing 99% improv and 1% gameplay. Turns out it doesn’t have to be like this.
• I also collect gemstones. Started as a kid when we came across an old quarz find on a hike. I was hooked by the shiny and have been collecting on and off ever since.

Painting miniatures, I'm new at this (less than one year) but I not so bad at this, and recently started to play street fighter 6 and really sucks buts is fun

Code golf on the cgcc stack exchange. I don't do it too often, but the community is pretty small and when I see a good one I can't stop thinking about it.

I'm really into calligraphy and snowboarding. Luckily there's a snowboarding presence here on lemmy, but I have not the time to start a calligraphy one.

I guess blacksmithing would be considered niche? Not doing it very regular. But once every view months.

Brickfilming! I make films with Lego using stop motion animation. Takes a lot of patience and my perfectionism is my worst enemy, but it's super rewarding, and there's a really cool community online around it. And yes, my profile picture is from my most recent Brickfilm!

Sing in chamber choirs

English change bell ringing

I collect plushies/stuffed animals (to the point where I'm running out of room for more) and I've played Tabletop RPG games like Pathfinder, Shadowrun and GURPS for a good few years.

Yarn dyeing started as a hobby and turned into my job quite quickly :)

It's fun and satisfying to see the colours evolve on yarn and how the colours act differently depending on the fibre blend you're dyeing.