Brilliant, thanks. It was made via displaycal and I do have the .ti3. I just did:
colorprof -v -as profilename
It worked, and it’s definitely faster in GIMP. It’s still a little slower than no profile at all, but I suppose that’s expected.
Compared to the LUT, the colors seem very close, though there is some shifting in the purple/red area… the main thing I notice is that the darker tones go noticeably darker using the matrix profile compared to the LUT.
Are there any other options I could/should include with colorprof to make things better?