You asked
Is the panasonic leica dg 100 400mm f 4 6 3 ii good for sports?
Yes, for outdoor sport, with one caveat. On Micro Four Thirds it frames like 200-800mm on full frame, and it's stabilised, so you can hold that reach steady. The catch is the aperture. At f/4-6.3 it gets darker as you zoom in, so it works best in bright daylight and struggles more in dim gyms or under floodlights. For sideline work, wildlife and sport points to 70-200mm to 100-400mm on full frame, so this lens sits at the long end of that range.
Good bodies to pair it with include the OM System OM-1 Mark II and the Panasonic Lumix G9 II. If you want to spend less, the Olympus OM-D E-M1 Mark III is a sensible option. Long lenses change hands a lot, so buying used can save you a good amount.
Written by Claude from this site's pages.