Dude at least 80% of these activities you listed cost a significant amount of money.
Musical instruments are the opposite of cheap, knitting materials and art materials (even the cheap stuff) costs money, you can’t legally form a NPO for free and you won’t be able to volunteer very well if you can only physically travel to the center of town on rural public transit or bicycle your way around a wide rural area.
The kind of biking and hiking at the amount of distance and time we are talking about isn’t free either, a decent bicycle that can do heavy mileage will cost money to buy and maintain. Plus all these sports will cause you to burn more calories necessitating more expenditures.
(Also have fun riding a bicycle everywhere on country roads with two narrow lanes and 55mph speed limits)
Cooking creatively for a group isn’t really a part of a $300 survival meal planning budget, and it’ll get pretty boring without some of the kitchen equipment that helps with that hobby.
In addition to that a lot of stuff that is cheap was not actually budgeted by the author of the article. In his example there’s no home internet or water budget, so even washing clothes or playing a game online isn’t in the budget.