[M T]

And yet we have almost no sense of how many of those "recovered" are not, and may not ever be, fully back to the health they had prior to coming down with COVID-19.

Some early evidence.  But I will point out that lung damage is only one symptom that may have long lasting consequences.   I believe there have been circulatory issues as well.  I've seen mention of mental issues. 

Lancet article

However, a 15-year follow-up study of 71 patients with SARS showed that interstitial abnormalities and functional decline recovered over the first 2 years following infection and then remained stable. At 15 years, 4·6% (SD 6·4%) of the lungs showed interstitial abnormality in patients who had been infected with SARS.

Follow-up outcomes are less well described in patients with MERS. In a study of 36 patients who had recovered from MERS, chest x-rays taken a median of 43 (range 32–320) days after hospital discharge showed abnormalities described as lung fibrosis in about a third of the patients.

Science News article

In 70 patients who survived COVID-19 pneumonia, 66 had some level of lung damage visible in CT scans taken before hospital discharge

[M T]

And yet we have almost no sense of how many of those "recovered" are not, and may not ever be, fully back to the health they had prior to coming down with COVID-19.

Some early evidence.  But I will point out that lung damage is only one symptom that may have long lasting consequences.   I believe there have been circulatory issues as well.  I've seen mention of mental issues. 

Lancet article

However, a 15-year follow-up study of 71 patients with SARS showed that interstitial abnormalities and functional decline recovered over the first 2 years following infection and then remained stable. At 15 years, 4·6% (SD 6·4%) of the lungs showed interstitial abnormality in patients who had been infected with SARS.

Follow-up outcomes are less well described in patients with MERS. In a study of 36 patients who had recovered from MERS, chest x-rays taken a median of 43 (range 32–320) days after hospital discharge showed abnormalities described as lung fibrosis in about a third of the patients.

Science News article

In 70 patients who survived COVID-19 pneumonia, 66 had some level of lung damage visible in CT scans taken before hospital discharge