https://www.health.harvard.edu/blog/the-tragedy-of-the-post-...
You can’t, because they don’t exist. You linked to the best there is, and it doesn’t rise to any reasonable standards of scientific evidence. Self-reported data is almost worthless. Uncontrolled, self-reported data is worthless.
I’m perfectly willing to believe you, but editorials won’t convince me.
There's a constellation of individually imperfect studies pointing in the exact same direction; that's basically how science happens. The studies exist in the first place because people observed Something Strange was happening, and wanted to quickly get a sense of severity and prevalence, to inform public health response.
And if you're not willing to update your priors, I'll be here waiting for the perfect study that proves long covid doesn't exist...
But anyway, some more material for you.
https://www.medrxiv.org/content/10.1101/2020.10.19.20214494v... https://www.bmj.com/content/370/bmj.m3026
It's going to be many years until we have a proper handle on this. Until then you might have to be willing to accept a flood of more anecdotal field data as having some analytical value.