Disc Golf.

Things that I like to do that can be done totally for free:

• Learn to read/write/listen to (classical) music (playing probably requires an instrument - not cheap, unless you choose to sing). There are plenty of open music theory textbooks online, I like this one. You can use MuseScore as a composition tool. Its playback and formatting (engraving) of the sheet music are very good. Additionally, if you want to try applying what you learn to pieces written by classical composers like Beethoven and Mozart, IMSLP has sheet music for over 200,000 pieces.

• Sudoku. You can use Hodoku to generate new puzzles and teach you new methods to solve them.

• Chess. Just google en passant. More helpfully, lichess is a ‘free/libre, open-source chess server’ that can teach you the basics of the game and pair you with other players in time formats ranging from 1 minute per player all the way up to 30 minutes per player, with 20 extra seconds per move. If you want to play IRL, a basic chess set is very cheap. Once you get into it, chesstempo is the best place for puzzles.

• Learn the basics of a new language with Duolingo or other similar websites.

These are just a few things you can do without spending a dime. If you’re willing to invest a little, the world is your oyster.

Over the last few years I’ve gotten back into reading books using my library app. Gardening can also be a low cost hobby if you are able to start plants from seeds and have some space outside.