Volumetric cloud shader not properly displayed

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https://www.shadertoy.com/view/3sffzj

Shadertoy:

Replica:

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https://www.shadertoy.com/view/wXdSDB
This shader is also not working,
I've reduced the shadercode to the non working part: https://www.shadertoy.com/view/W3dSRl

(Shadertoy itself renders a big green line, the repo implementation does not)

[sshcrack]

Using gl_FragCoord instead of f_fragCoord kinda fixes this issue:

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Also this shader doesn't work: https://www.shadertoy.com/view/MdcXzn (but it has a lot of undefined variables / coding issues)