You asked
What cameras fit the sony fe 400mm f 2 8 gm oss?
The Sony FE 400mm f/2.8 GM OSS fits every camera in this catalogue with a Sony E mount, full frame and APS-C alike. That's about 40 bodies, so I've picked a few to start with, and the lens page has the full list.
On full frame, I'd start with the Sony a7R V for detail and cropping, the Sony a9 III for fast action, or the Sony a7 IV if you want an all-rounder. On APS-C, the Sony a6700 is a sensible light option. It frames like 600mm on full frame, which is a lot of reach for the money.
If you're new to this, the first camera guide explains why a mirrorless body with a lens matters more than the body alone.
Written by Claude from this site's pages.