Piñatex (Spanish pronunciation: [piɲaˈteks]) is the trade name for a non-biodegradable leather alternative made from cellulose fibres extracted from pineapple leaves, PLA (polylactic acid), and petroleum-based resin

Still plastic, unfortunately.

Cork is definitely a cleaner alternative, but I don't know how durable it is in "leather" form.

Cork is cork, a lovely and great material with a ton of applications, but it's not leather. It will not last as long and won't withstand the abuse that leather can.

Piñatex (Spanish pronunciation: [piɲaˈteks]) is the trade name for a non-biodegradable leather alternative made from cellulose fibres extracted from pineapple leaves, PLA (polylactic acid), and petroleum-based resin

So, basically when the fibers decompose, it leaves PLA and petroleum byproducts.

PLA, is a plastic. A bioplastic, sure, but contrary to popular belief, it will not degrade unless done under industrial composting conditions. It will not degrade in your backyard compost pile, and will break into microplastics.