It should still work (ferrite core method) but as far as I know nobody else has tested it yet using an 8KX with the fibre-optic cable.
The important thing to do is loop the all on one section of the cable through 4-6 times, through 4 of the ferrite rings. This provides sufficient EMI supression to eliminate it. If it doesn’t work it’s usually because people use the wrong ferrites, or forget to loop it through several times etc; if done correctly it definitely works on pimax 5k+, 8k, OG Vive, cosmos and Index. I haven’t seen anyone do it with an 8kx yet but I would be surprised if it didn’t work as it uses the same tracking system.
By the way, regardless of emi if you cover the sides of your HMD, for instance with your hands it will grey out because it loses tracking. Just making sure someone doesn’t confuse EMI related issues with general loss of tracking from blocked sensors. It will come straight back though when you move the obstruction away where EMI isn’t the problem.