Biking. When I was undergoing cancer treatment I bought an e-bike with 5 levels of pedal assist: none, 10%, 25%. 50% and full. It was my “emergency plan” if I got hit with a bout of fatigue and eased the worry that if I rode too far I’d be too tired to bike home. I normally ride 20-30 miles so while in treatment I would do 10 miles with no assist, then switch to 10%. Only needed higher assist a couple times.