The wording of the thirteenth amendment is very specific.
Neither slavery nor involuntary servitude, EXCEPT as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Except as a punishment for a crime.
Reading the book Steel Driving Man by Scott Reynolds Nelson, about the REAL John Henry made me think of this. The book spends a lot of time describing the building of the Ohio Connecticut railway, and how many African Americans during the emerging Jim Crow south were picked up on felonies that used to be misdemeanors. What should have been a small fine ceded up in months or years of hard labor. The growing prison population allowed large corporations like the Rail Roads in the United States to take advantage of prison labor as slave labor had been used in the past.
Unfortunately, it's quite late here in the UK and I don't have the time to actually substantially address the full thrust of your question, which seems to be concentrated around the phenomenon of prison labour.
What I will do for the moment is direct you to a previous, detailed answer I've given on the subject of indentured servitude, and why it differs from slavery. That answer starts here and runs to three parts, though you may have to expand a collapsed comment to see Parts 2 and 3. Part 1 is a critical refutation of a source the person I'm responding to linked to, whilst Parts 2 and 3 deal more substantially with the differences between slaves and indentured servants in North American history.
The summary is that historians are in broad agreement that indentured servitude as it was practised in North America was not a form of slavery. We generally distinguish between a concept we usually refer to as 'unfree labour' and slavery; slavery is a form of unfree labour, but not all forms of unfree labour are slavery. Rather, slavery represents a particular and extreme form of unfree labour that has manifested itself in several contexts throughout Human history. Prison labour as it has historically been utilised in the United States is generally conceived to be its own form of unfree labour distinct from both slavery and indentured servitude. In that context, the 13th amendment very much abolished slavery, which was a distinctive system with a unique construction, whilst still legitimising others forms of unfree labour.
If you would still like me to talk more to the subject in depth tomorrow, I would be happy to do so - simply notify me in a reply what you would like me to talk about specifically, either in your original question here that still feels unresolved (prison labour, perhaps) or in response to the linked answer about indentured servitude, and I will find the time to give you a reply tomorrow.