I was incarcerated from Feb 2017 to Jan 2018. Five of those months were spent in Edgecombe County Jail, six months in Albemarle District Jail, and a few nights in Wake County Jail (downtown location, not Hammond Road). The reason for moving around is because I was a Federal detainee. The Federal government contracts with various local jails for housing prior to being transferred to a permanent facility post-sentencing, release, or deportation. In the three locations I named, there are limited opportunities for State inmates to work, and none for Federal ones. Despite this, people found ways to earn an income. The article touched on some of those ways, but many went unmentioned. Here are hustles that I have firsthand knowledge of:

Bookie, football pool: I inherited this game from Jakym Tibbs in Albemarle. The way it worked is that players would pay a $1-equivalent commissary item in exchange for an entry slip. On the slip they would select the winning teams from each Sunday NFL matchup, and an exact total score from a specific matchup as a tiebreaker. I collected the slips and commissary, and then recorded it onto a master sheet. I would take a cut of the prize pool. It was practically no income, just for some Sunday fun.

Tattooist, stick and poke: Ink can be created from soot or sourced from a flex-pen[0] and a staple or other small piece of metal will serve as a needle. Sell tattoos.

Tattooist, tattoo gun. Create a tattoo gun using a motor from a beard trimmer, a toothbrush, and a straightened and sharpened spring from an illicit ballpoint pen. This tool allows for much larger and more lucrative works, but is harder to conceal. Sell tattoos.

Vinter: Prison wine is called "Buck" in the North Carolina system. Buck is made by combining some bread, fruits, and a generous helping of sugar procured via Trustees. For small batches of Buck you can ferment it in individual bottles. For larger batches, double up a couple of clean garbage bags. You can make gallons of Buck this way, and then distribute it into bottles after it has finished fermenting. Sell the resulting product.

Pharmacist: Drugs can be smuggled into a jail via a corrupt guard, an inmate[1] entering from the street, or the mail. As for the mail, Suboxone strips are small enough to conceal in a letter. Practically anything else can be obtained by way of guards or inmates from outside. For rolling papers they would impregnate normal paper with a coffee mixture and then dry that out and use it for smoking marijuana. Obtain drugs and sell them for a markup.

Porn Merchant: Pornography is prohibited and so there is a market for it. You can rent or sell single pornographic images or an entire magazine of it.

Tailor: In Edgecombe the dress code was lax, and destruction of jumpsuits was not punished. Jumpsuits can be modified into a two-piece outfit, which allows for better range of motion. This makes your outfit more comfortable and is advantageous in fights. Obtain a razor or other sharpened blade and cut a jumpsuit in half at the waist. Cut vertical slits around the top of the shorts/pants and then run a string through those slits to act as a belt. Charge for this service.

Poker Dealer/Player: Poker chips were created by ripping up a deck of cards. The dealer took a percentage of the buy-in, and also played at the table. Cheating is met with violence.

Spades Player: You and a partner learn how to play Spades and go try your hand at the table. The buy-in to a game of Spades was a $1-equivalent commissary item. Some people would play this for 5+ hours a day, round after round, back to back to back, without speaking a word.

You also had thieves and strong arm robbers. If someone stole from you then you would have to meet it with violence, "check off" (get yourself transferred out of the unit), or become a target of increased predation.

I think I've basically covered everything that I encountered as far as money-making goes. The cooking, haircutting, and laundry side-hustles basically worked as described in the article.

Edit: Thought of some more! Artist, weaver, and hair braiding. The weaver created and sold little bracelets with designs on them. The artists took commissions, and the braiders did hair.

[0] Pen in a flexible, translucent rubber casing. See Shomer-Tec Prison Pen. While you could make the barrel wide enough to comfortably write with, the ballpoint tips on these are completely worthless.

[1] In the prisons you have green-clothes and brown-clothes, low and high security. I am told that some in green-clothes are eligible for employment in state services outside of the facility. Groundskeeping at the state ferry system, for example. During your work detail you can collect a parcel of contraband and then smuggle it back into the facility. It is then sold.