If I use Medicham V's "Yoga Loop" attack to KO one of my opponent’s Pokemon, per the effect I get to take another new turn. If I then play Pokemon Ranger, can I use "Yoga Loop" again?
No, Pokemon Ranger won't bypass the repeat limitation of Yoga Loop because that is not an Attack Effect, it is a Game State Check. Yoga Loop is checking what the game state was in the past (did you use it last turn?), and Pokemon Ranger has no effect on that.
Source: TPCi Rules Team (2021-09-23)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH7_83
SWSH7_83
XY11_104