Today, a graphics fix made its way into the official #FreeBSD 14 pkg repo.
I'm not entirely sure which package the perpetrator was, but likely one of libdrm, mesa-libs and mesa-dri.
This fixes an issue where elements on screen wouldn't get updated when the mouse was moving.
This made blender unusable for me for *months* and was finally fixed after today's update.
So, if you had similar issues (especially with an amdgpu-driven card) try updating – things just might work after that. :)