The #TennisAtHome series has taken off in the time of the COVID-19 crisis. With that comes a host of tutorials, remote and/or properly socially distanced, on a range of topics. You can learn spin, slice, and other plays on the ball in the privacy of your own backyard, playing against a wall. (Really, any wall will do at this point to satiate the need to play some version of tennis.)
The USTA has a fantastic new footwork drill, with a run time going on 6 minutes, that provides a cardio workout and a hook—it was inspired by Stefanie Graf, or Steffi Graf as she was known in her pro playing days.