LC is not like training for a 5K run, it is more like being run over by a train after a 5K walk. I got covid last March on a 7-day 350 bike tour. I normally bike ~7000 mi/year. The LC hit after covid, and I went from biking up to 80 mi/day to 5 mi on an exercise bike with a nap afterwards. My LC went away after 8 months. LC hits endurance and once you are depleted, the recovery is much slower than before. So, I would exercise in snippets (5 mi), rest for a while, then bike or walk a bit, and rest, and all at levels that would not trigger the LC fatigue (also termed PEM). On a happier note, LC doesn't seem to hit resistance training, so if your husband is fine with you lifting weights or other (nonaerobic) exercise then you can still keep your muscle mass and bone density until you are over LC. Make sure you get enough sleep and avoid stress; those hit LC as well. Food intolerances can be triggered too, so consider keeping a food log.