After some time, you can scrape off all the poly stuff, leaving you with just a cotton chair, or what's left from the bonding material from the PU leather. You can accelerate the decaying process by leaving in the sun.

At that point, you can just either leave it be as a cotton chair, or buy some real leather and glue it to the chair. Based on picture 5, there's a high chance that the bonding material from the original PU leather is enough to be bonded to new original leather.

Its legit, I got an old chair, the PU starts peeling off, after some time the PU all brittle, I just scrapped them off. Still got a nice cotton bonding layer underneath. I just use it as it is. Don't force scrape them or you'll risk the underlying bonding material to rip off as well.

By the way, I don't know what's the bonding material for the PU leather on your chair. It could be thick, it could be thin. Its good if its thick.

You can get leathers from Mega Leather Shop. You can go for new one, or you can go for the leftover stock (cheap old stuff). But real leather don't disintegrate like PU leather does, so its okay to go for that if you don't mind the cosmetics. You gotta to DIY it yourself though.