Displacement is blocky I am trying to do some Moon renders using NASA's CGI Moon Kit: https://svs.gsfc.nasa.gov/4720

Said kit has super high-res color and displacement textures (27000x13000), but this is what I'm getting up close:

Is there a way to smooth it out?
Even though a 27k displacement texture which weighs 1,06 GB shouldn't even look like that in the first place...
Shade Smooth is (of course) enabled. Auto Smooth is off.
I tried adding a bunch of Subdivision Surface modifiers, but they didn't help at all.
Someone said I should use Adaptive Subdivision, but I couldn't find it in the Subdivision Surface modifier panel.
I also tried plugging the same displacement texture in the Normal input of the Principled BSDF through a Bump node, but the result was even worse.
Please help me!
These lines are visible also in the original texture. So to get rid of this you would have to use some image editor to compensate it. Here I used Photoshop's Box Blur filter with range 1 px that wasn't enough so I used it twice, but you loose some details.
Original

Box Blur 1 px

Box Blur 1 px applied twice


There are probably better algorithms for reconstruction or pattern removal like some FFT Fast - Fourier Transform (they are like a magic in some cases) ... so here are some examples

https://www.youtube.com/watch?v=D9ziTuJ3OCw
https://www.wirebiters.com/salt-pepper-image-denoising-using-matlab/
https://www.cs.unm.edu/~brayer/vision/fourier.html

Ten years ago I used some FFT script for Photoshop, but it is too far to remember anything, sorry :)