Then I was recommended to change the color profile from a LUT-based to a matrix-based one, and it solved the problem. Is this something that also applies to Lightroom 6?
Never incurred those problems in any Mac running Lion through El Capitan.
If, as you say, you found a solution that works well with LR 5, is there any reason why you can't try the 30 day trial of LR 6, instead of seeking opinions from others which may or may not be relevant to your case?
LR6 and PS CC, both latest versions produce identical previews on 10.11.2 with NEC SpectraView. One must preview at 100% and do so in Develop: