I know of only one decentralised Stable Coin but you've never heard of it and it is very small with limited amounts on the open market.

Fortunately for me I'm getting paid with it and it's relatively easy to convert it to anything else including moving it to my credit card to spend.

Lightning wouldn't help it though because it already has free instant transactions without limits so I'm not sure what purpose there would be wrapping it in lightning. I'm struggling to understand what a "stable coin on lightning" means when you can already flip these things around at minimal costs and very quickly.