If anyone's looking for really gentle or disability friendly exercise...
Doctor Jo on YouTube is a physical therapist who offers lots of therapeutic stretching and exercise videos for specific conditions and pain relief. [x]
Leap Services is a Canadian physical therapy group that has a YouTube playlist of gentle exercise routines. All of these exercises are done in a chair (except for one which is done on the floor) and are intentionally adaptable to different bodies and needs. [x]
Yoga with Zelinda on YouTube has yoga that's adapted to a large number of conditions, for instance, providing a playlist of routines that don't require kneeling and another of chair yoga. She also offers yoga for specific health challenges, like fibromyalgia and mobility issues. There's a playlist of yoga routines for people with bigger bodies as well. [x]
Santosha Spirit on YouTube has yoga routines for people with chronic fatigue, chronic pain, POTS, and EDS. [x]
Yoga with Shaunneka on YouTube has a playlist of slow seated yoga, including chair yoga, as well as a playlist of gentle yoga. [x]
Qinergy on YouTube has tai chi sets broken down into easy tutorials. There is a seated version of her shibashi set. [x]
Perth Tai Chi Academy on YouTube is similar to Qinergy. It provides a seated version of daoyin yangshen qigong. [x]