Perlin noise on a plane, can be either in line with the camera or off at an angle. Nice effect. Very easy. I don't even count myself as a proper artist.
Clouds can obviously be hard when you have a specific cloud formation in mind — but "just" a random cloud, to the standards of most who will observe it, is much easier.
And of course, there are plenty of free photographs of clouds, and Photoshop has had plenty of filters — even from the days before people had broadband, let alone what people now call AI — to turn those photographs into different styles.