Slightly flaking leather office chair

The arms are often fairly generic. When the arms on mine disintegrated, I got new ones cheaply from (I think) Chair Doctor.

I would guess th 'leather' chair bought from Costco is actually covered in reconstituted leather or worse 'Artificial leather, also called synthetic leather, is a material intended to substitute for leather in upholstery, clothing, footwear, and other uses where a leather-like finish is desired but the actual material is cost prohibitive or unsuitable. Artificial leather is known under many names, including leatherette, imitation leather, faux leather, vegan leather, PU leather, and pleather' Thank you Wiki

You could try a leather dressing it will soften leather if it is hardening

Bonded leather

My "leather" chair appears to have a thin layer of vinyl on top, which mostly came off during lockdown when I was using it a lot.

The seat appears to be polishing up as if it is real leather.

I just put up with the suede effect. I can't replace it; it was bought with the last birthday money my father gave me before he died.

Andy

Very possible to re upholster with real leather....