I happen to know about job training for incarcerated folks through a family member and also working with an adult basic education program. At least in the USA, the number of incarcerated people who happen to have coding skills of any level is going to be small, like very small.
The vast, vast majority of incarcerated people need basic skills training to even be able to look for a job. Functional illiteracy is high, most have at best a grade-school level of reading/writing and math skills. There are many reasons why folks end up in jail, typically for each person a multitude of things went sideways early in life. One of the most common of these is a completely derailed education. It's never too late of course, and most people getting out of jail are still in their 20's and 30's.
They're hungry for legit work, so yeah, there's enormous untapped potential. The organizations working in this space get government and private funding but are always on the verge of vaporizing. They are, AFAIK, non-profits with very strong social-work, basic-education, traditional vo-tech focus (because that's what their clients need most).
This 100%. Basic literacy & numeracy is stunningly low in UK prisons & improving basic education has been shown to improve reoffending rates greatly, in policy terms it ought to be a no-brainer but as you say the NGOs & charities in this space are starved of cash, mental health & addiction charities would slash offending rates, - but the government throws hundreds of millions of £ at contractors like Serco & G4S who can afford to lobby hard & donate to party funds, but who squander it.
