I use 6D mark II to shoot interview video because it is an inexpensive camera that allows blurring the background when used with fast prime lenses.

There are just a few problems:
(1) low dynamic range
(2) a higher contrast look than video shot with a camcorder (sony FDR AX100)
(3) focus hunting when using face tracking, even when the face is bright and clear and not moving much

What color space does it use for video? It seems to have higher contrast than rec 709 video produced by the camcorder, and there seems to be no way to change the video colorspace.
I think this higher contrast also contributes to its lower dynamic range. It's like recording audio with a higher gain -- the audio is more likely to clip.

All 3 problems seems like fixable in firmware, making this old camera way more useful. But there is no such fix from canon, and no 3rd party firmware (magic lantern) for this camera. Why fix an old camera when you can sell a new camera, right?

I guess buying a R6 would solve at least the first 2 problems. That's $2500 per camera and I need a multi camera setup. Is there a cheaper solution?

A Canon EOS-90D. You’d have to compromise on your full-frame sensor. The APS-C sensor on a 90D is very close to Super35. At least you would have a camera designed for video.

It’s not only sensor size that affects available shallow Depth of Field…