Are Ryanair contractors in Spain entitled to use Spanish social security?
YOU are entitled to anything that YOU sign up for and YOU pay for. Since all the down sides are to YOU and all the benefits to your contracted party called RYR....
In short YOU will be screwed at some point if YOU get a situation when YOU cannot work when YOU are sick or disabled or if YOU have not paid enough into your pension... As soon as that happens the contracting party RYR has no obligation to YOU...
So as long as YOU intend not to get sick or disabled it is fine....