Edit: I don’t mean to imply the author isn’t paid fairly by Turso. A few posts down, the CEO of Turso asserts that they do pay fairly. The OP in this thread might reasonably wonder about this because several states do in fact use prisoners as unpaid slave labor.
In practice, only "involuntary servitude" has been used. "Community service" - unpaid - is a very common low level sentence.
The eighth and fourteenth amendments almost certainly forbid enslavement - permanently becoming human property - as a criminal sentence.
Even before the 13th amendment, enslavement as a punishment not common, if it happened at all.
There is almost no case law on the 13th amendment. There are no legal slaves in the US today, and there have not been since the 19th century.
https://theappeal.org/louisiana-prisoners-demand-an-end-to-m...
If you can lock someone up and get close to free labor for it, then we're going to start locking a lot of people up. I mean, it's free labor. Which is why we used to give people 20 years for possession of marijuana. What, you think it's just a coincidence we were throwing primarily black Americans away in prison for ludicrous amounts of time where they'll spend their days picking cotton?
That's what happens when imprisoning people is cheap.