LUTs showing up differently on two different computers

First, it is CRUCIAL where those LUTs are parked on the computer. They should NOT be in the Premiere Pro folder's LUT folder, with the LUTs included in the apps. As LUTs in those folders are accessed not specifically by name, but ONLY by relative location in the folder ... eg, "fourth LUT in the alpha-numerically sorted list of the folder" ...

So you may actually be getting a different LUT than expected if you park the LUT in the Premiere Pro folder tree.

A good place for User LUTs is in the Program Files (Package Files on Macs)/Adobe/Common/LUTs folder tree. Within that, things in the Input folder will be listed in the dropdown for Input CM in the Project panel; LUTs in the Technical folder will be listed in Lumetri's Basic Tab dropdown; and things in the Creative folder will be seen in the Creative tab's dropdown list.

Second, you both need to make sure your monitors are set to the same thing ... which for most editing is STILL Rec.709. Work with Rec.709 sequences. And if any clips are log-encoded or HLG, you need to use the color management options in the Project panel's right-click/Modify/Interpret Footage dialog. I can go into that in more detail if you need.

Third, unless you know you have a tightly-calibrated Rec.709 monitor ... which is highly doubtful ... you need to set the Preferences option for Display Color Management to 'on' by clicking in it. Especially on Macs ...

Fouth, outside of Premiere on a Mac, the ColorSync CM utility applies an incorrect gamma to the display of Rec.709 video, making it appear lighter (especially in the shadows) and less saturated than within Premiere. Premiere's "view" is actually far more accurate, as they work to keep within the Rec.709 specifications. That may be in play especially if you're viewing things outside of Premiere and one is PC and the other Mac.

Fifth ... make sure you have clip CM set to the same thing on both computers. Check with the clip Properties in the Project panel. To change things, still in the Project panel, right-click/Modify/Interpret Footage and use the CM controls at the bottom.

Neil

Do you have identical monitors, color spaces, and calibrations?

See if this helps:

Understanding Color Spaces, HDR, and what that might mean to you
https://www.youtube.com/watch?v=odwptnEhxJs