The chinese did some good reports on ME/CFS prevalence after Sars. About 50% of everyone who got Sars had linger symptoms initially after recovering from the acute phase and around 10% of everyone still had ME/CFS about 12 months later, none of which have recovered from that, but a few did die. There are at least 3 papers on it, I went through them just as Covid19 was kicking off.

Covid19 produces somewhat less commonly lingering symptoms compared to Sars and less severely but no where near as much as we might like (more like 5% long term).

Yes! I don't have the link here now, but lingering symptoms are common after a viral infection; the one that I saw said that the incidence of some flu symptom remaining months after infection is as high as 40%.