Do we have reason to believe that lingering fatigue, cough, etc. is a real thing? We do. Any serious infection can cause these things, and (as quoted in the article) some experts in the area say they're more common and severe than would normally be expected.

Do we have reason to believe that Covid causes some crippling disability that can never be treated or recovered from? Not strong ones, although of course even weak and inconclusive evidence should be investigated with a novel disease.