* rock climbing is great (for myriad reasons), but it really forces you to use pretty much every muscle in your body. This is especially true for the muscles you use to actuate key presses, which are the primary gripping muscles in climbing
* use an erg (indoor rowing) machine. After long bouts on it (which is a fantastic low-impact cardio sport too), your grip / grasping muscles on the handle will strengthen a lot
* balance this out with some flexion motions, which one can do with yoga (e.g. think your hands during downward dog). If you don't have time for yoga, you can "habit hack" it into your life in easy ways: yin yoga is basically "holding yoga positions for a long time", and once you learn the basic positions it is easy to do them during a meeting (remote, via Zoom or whatever) or when you're watching something for leisure