Howto convert a Shadertoy shader to a pixijs v6 shader/filter

The issue is in how you are passing the uniform values to the shader. It's fixed by removing the wrapping object:

var width = window.innerWidth;
var height = window.innerHeight;
const uniforms = {
    iResolution: [width, height],
    iTime: 0
};

As you can see in the examples, in PIXI version 5 and above you don't need to declare the uniforms in objects with type and value. This can also be found in the migration guide.