okay, well, others with relevant qualifications are saying it DOES exist, so since nobody seems to be saying it doesn't, I guess we can go with their expert conclusions.
Pretty much anything public health people say on the topic of COVID turns out to be wrong on close inspection. It's really astounding. Even very basic things like getting an actual clinical definition of COVID itself (let alone long COVID) turns out to be impossible, which is why the official definition governments use is "got a positive on a COVID test". That's not actually a disease symptom but COVID isn't defined by symptoms any more than long COVID is.
The reason this happens is that public health is an authoritarian collectivist concept - the government will make decisions for the collective good even if individuals must suffer as a consequence. The entire culture of that space is dominated by a mindset that says, "we will obtain compliance by making scientific sounding claims, because people respect science and will follow it". That's why COVID research is so full of conflicting and nonsensical claims.