Mine would be creating pen and paper ciphers for my made up secret communication needs.
Contributing to localization in my language. (I use Localizor or weblate) I’ve helped translation for the Godot Engine and many released games. It’s a free hobby granted you have a PC and some knowledge. I’ve always liked translating stuff for those who can’t speak English. And it keeps my language skills sharp in both.
For me it’s being a witch and all witchcraft related things.
I collect photos of sidewalk stamps and try to find as many years (and weird, different, unique stamps) that I can.
http://photos.rasterweb.net/index.php?/category/30
I’m a contortionist.
i collect post apocalyptic books, espicially zombie related books. most are the audio version, my wife swears she will divorce me if i buy any more books, lol