Unity .cube LUT Specs

Hi, has anyone had problems applying .cube LUTs in PP2 color grading? In Unity 2020.3.31f (Built-in Pipeline, Post Processing Stack v3.2.1), Unity seems to interpret the LUTs with the wrong brightness scale or perhaps opposite brightness (reverse from light to dark).

Images are below.

I'm using standard basic industry-accepted .cube LUTs, and in all other professional software they work fine.

But in Unity 2020.3, when I am choosing "External" under PP2 color grading and applying professional .cube LUTs, they are not applied "correctly". I've tested multiple LUTs. Radical misapplication happens, as if Unity is reading the .cube format incorrectly.

The .cube size I am using is 33x33x33

I was going to upload the images, but Unity Answers chokes on any link or image today, LoL.