Does it all fall down to there is no one accepted definition of sport.
For me:
Physical activity that involves skill
Is competitive
Agreed rules and regulations
It needs both. So going for a run is exercise, entering a race would move it to a sport.
Chess requires skill but not physical activity - not a sport.
Darts requires skill and some physical activity - so I would err on the sport side
Ballet - physical activity and skill not competitive and doesn’t have a set of rules and regulations - not a sport.
Cheer display (at a match or otherwise) physical activity and skill but not competitive and no set of rules/ regulations - not a sport
Cheer competition teams - ticks for all three, so a sport.
(Strictly isn’t a sport in my mind as they don’t stick to the rules and regulations regarding the dances and pretty much have an anything goes appraoch)