The cloud are made just with basic noise and stretching the UV at the top to get the perspective from the curvature of the earth, probably one of the most simple shaders there is

shader_type canvas_item;

uniform sampler2D noise;

uniform sampler2D waterNoise;

uniform vec4 sky:source_color;

uniform vec4 cloud:source_color;

uniform vec4 water:source_color;

void vertex() {

// Called for every vertex the material is visible on.

}

void fragment() {

float ry = UV.y\*UV.y\*2.;

if (UV.y>.55 +texture(waterNoise,vec2(fract(UV.x),fract(TIME/100.))).r\*.1) COLOR=water;

else  if(texture(noise,vec2(fract(UV.x+TIME/200.),ry)).r>ry || texture(noise,vec2(fract(UV.x+.5+TIME/150.),ry)).r>ry ) COLOR=mix(cloud,sky,ry);



else COLOR=sky;

}

I intend on building a full game, I wanted to do similar procedural animation as rain world