Something made for upholstery. Most blankets are made to be comfy rather than animal resistant. But most upholstery fabrics will hold up under anything but claw sharpening and be easier to clean overall (because you can blot up most stains as opposed to having to wash them).

Avoid thin quilted blankets if you absolutely have to go that route. You’ll likely want woven rather than knitted as knit fabrics are stretchier, and thus more prone to working loose fast.

Wool actually does rather well for this, but holy shit would that be expensive. Worse than the purpose made covers.

Tbh, going with throw blankets is often as good as or better than covers. Depends on exactly what your goal is, but throws can be tucked around cushions as well as other sections. Most throws are thick and knit, but they’re thick enough that being knit isn’t as difficult to deal with. And still likely to be less annoying than a knit blanket turned into a cover.