Trying to come back from it myself. Tested positive ~2.5 weeks ago (but had another respiratory infection for 3-4 weeks before that which I'd been trying to ride through - it's been a crappy winter for training). Once I tested positive, I took the next 2 weeks off - had thought about riding on Zwift the next night because my team had a race and I didn't want them to ride shorthanded (a Z2 finish in dead last would have been more series points than not riding), but I got dizzy and lightheaded halfway down the stairs to the basement where my trainer is and I I got scared of falling off the bike and hurting myself so I slowly dragged myself back up the stairs.
After 2 weeks off, I was down 5-6 pounds (hooray!!!), and tried hopping on the bike with a nice easy warm up and then a 30-40 minute race on Zwift to see where my fitness was. When warming up, my hr was about 10 bpm higher than expected given the effort I was putting out. Zwift race was similar - ~10 bpm higher than I should have been given the effort, ended up sitting up after repeatedly hitting max hr on little surges in the first 6-8 km until I couldn't hang anymore. Since then, I've tried a couple of easy z1/z2 rides to just see if I could get my legs moving again. HR is still higher than it should be, but maybe not 10 bpm up on low Z2 power. Eventually, I end up losing my patience and pushing harder than I should and finding my limit, which is lower than it was 3 weeks ago. I had been planning on starting a training block this week, but that's going to be pushed back a couple of weeks so that I can find a semi-accurate baseline before starting.