Reading or chess are pretty cheap.

I just want to point out that any hobby you engage in for entertainment without it feeling like a chore is by definition not boring (to you). Personally I couldn’t see myself in a situation where I’d be collecting stamps, because I would probably find it very boring. But others enjoy it, so it’s a valid un-boring hobby, just not for me.

Learn a language. This basically morphs into other hobbies, like reading or listening to stuff. But it’s gratifying.

Video games - but a little different from other suggestions, get really deep into a game. Learning to play some games is a hobby in itself. Speedrun your favorite, get into your local fighting game scene or play Fightcade, get Slippi and play Melee online, go for high scores in some shmups, competitive Tetris or Puyo Puyo. Etc etc (Though re-reading op, I guess a lot of these may have unreasonable learning curves)

May I suggest simple crafting, like whittling, ancient/native pottery, wood carving, paper basket weaving, origami, crochet (or the slightly more addictive and expensive knitting), braiding, weaving, macrame, yarn spinning, decorative knotworking, flower pressing, dyemaking, hand dying, flower arrangement, make walking canes, etc?

Or maybe an instrument? Someone mentioned guitar, but why not harmonica, ukulele, bongos, simple percussives, or why not take up singing, there’s typically a choir almost everywhere, or you could try solo, or whistling, or yodeling.

Or maybe take up gardening/growing? In pots, hydroponically, maybe on a growing lot, or someone’s yard?

Or take up community projects, like either sanctioned or guerilla gardening, greening, forestry, litter picking, maintaining communal spaces, volunteer, start a community project (pollination diversity, bee keeping, growing lots, food drive, food forestry)

Or take up a cause? Build community, take affirmative action, demonstrate, protest, coordinate, communicate, with an established org, or on your own?

Maybe the outdoors could entice? Take up walking, ornithology, watch bats, discover new insects, take up chabana/ikebana, learn to forage, learn survival skills, go hiking, stack rocks, track animals, learn trapping, get into scouting, make bark boats, learn to skip rocks, climb trees, jump in puddles, pretend (or practice) animistic rituals, feel rain on naked skin, sleep under a bare sky, pick skulls, horns and bones to craft with.

Perhaps create stories, tell stories, write poetry, learn magic, juggle, poi, take up clowning, go swing/country/folk/traditional/ballroom/social dancing, try Butoh, write sketches, join a theatre, start a business, take up decorating, or just embrace whimsy?

I can also warmly recommend trying a new thing every week/month/period and see what sticks and not.

If it doesn’t have to be social, you could try programming. It’s easy to start and the satisfaction of having built something is an welcome extra

Zero cost:

• Running
• Yoga
• Bodyweight exercise

Zero cost if you have a library card:

• Reading (fiction)
• Reading (non-fiction)
• Online discussion

Price of pencil and paper:

• Writing (creative)
• Writing (journaling)
• Drawing

Fairly cheap:

• Music (playing)
• Music (listening)
• Painting

Origami. Very cheap to begin with, still cheap when you’re deep into it. Unless you got so deep that you’re travelling the world to go to conventions but that’s another story, the biggest expense is buying books once you decide to have them physically.

Don’t use printer paper, kraft paper is cheap and works perfectly. Only down side is having to cut it.

Explore your neighborhood

• geocaching
• contributing to open street maps (Street complete)
• photography with your cell phone

Reading. You got a library near you? Great, you’re set. You don’t have a library near you? E-books.

Cycling: Get a bicycle and start exploring your area. It doesn’t need to be a nice bike; check garage sales and Craigslist and get whatever fits comfortably. Wander off your usual routes and you will encounter new corners of your town that you never knew existed.

Music: Pick up a used acoustic guitar, electric keyboard, banjo, or whatever you can find. The world is full of inexpensive books and free YouTube videos to teach new students.

Drawing: Make doodles, little comics, or sketches of whatever is around you. A pencil and paper are all you need. Look up YouTube videos for daily sketching practice exercises.

Amateur radio: An entry-level license involves a basic quiz and a nominal fee. Cheap radios can be had for less than US$100. If you meet an old timer with a garage full of gear they might hand you a pile of old equipment for free.

Of course, any of these can become expensive and time-consuming hobbies if you go down the rabbit hole. But that just means you have found something you love.

There are exactly zero boring hobbies, through the right eyes or right lens.

boring as you use it, is a term which works best when describing a person. Take from that what you will.

That’s very little to go on, so my suggestively is reading.
Very cheap to get into as well as something that’s is easy to pickup and let rest. Plenty of free options around too.

If you have a mediocre PC there are a ton of non-graphically intensive cheap indie games on steam. Rimworld is $30. Stuff like VR Chat is free.

Honestly, photography.

You probably already have a smartphone with a decent camera.

Start experimenting with framing, focusing, and other settings.

You can get some great photos with a smartphone

Electric drum kit is fun, cathartic, and quiet outside your headphones. Chilis are easy to grow, and they certainly entertain the mouth. Running saved my life. Tennis balls from the machine launcher. Rock wall. Skateboard. People love pickleball, but you need friends. Darts. 3D printer. Electric piano. Cooking class you can meet a girl, cook for her, get back rubs. Singing lessons. Fetish exploration. You got this.