i'm fortunate to not have had it, but a buddy of mine had it recently in late Feb, he was off for 2 weeks, did 5hrs easy first week back, 5hrs (2 rides) 2nd week back, 7hrs last week with a few more efforts, and this past Tuesday he did an FTP test and smashed it and has a higher FTP than before covid lol I think the key is just to take time to get over the illness and gradually get back to reintroducing activity