Getting reasonable exercise with as many worn out parts as I have is not an easy task, so I rely on our Personal Trainer - Fritzie the dog. Getting past 75 has been a lot less troublesome with a couple daily dog walks. Dogs are perpetual 3-year-old children - they want to be outside doing stuff, need to stop and examine everything (which slows down the action to a doable level) and leads to pleasant interaction with other dog walkers. Best of all, unless you're in a big city, not even Covid interfers with your daily workout, and in the winter, wearing a mask is both a way to stay safe from the virus AND be kind to your lungs in the northern climes.
Daily walks with my dog are one of the things keeping me going during this stressful and difficult time. Yoga is another good exercise that doesn't have to be challenging, and it has many health benefits as well. It stimulates the brain, improves strength and balance, and can also help reset your nervous system.
It's good to hear you're doing this! Walking a dog gives all sorts mental health benefits, too. The love one feels for their furry friend releases all sorts of good endorphins, the attention it takes to keep an eye on the dog stimulates and exercises the brain, and the (generally) good responses from neighbors builds a feeling of connection which is critical for mental well-being, especially now.