You asked
Best camera for the sigma 20 200mm f 3 5 6 3 dg contemporary?
The Sigma 20-200mm is a full-frame travel zoom, so I'd start with a full-frame body. My pick is the Sony a7 IV as a sensible all-rounder. If you want the most resolution to crop into, the Sony a7R V is the one.
If you'd rather travel light, the Sony a6700 is a good match. On APS-C the lens frames like 30-300mm, which gives you real reach in a small body. For more on that trade-off, see the travel picks.
The lens isn't stabilised and it gets darker as you zoom in, so good light or a steady hand matters at the long end.
Written by Claude from this site's pages.