It works fine through GM:S 1.4 on a Xiaomi MI4c, which isn't really a high-end phone.
If the demo doesn't work, your device is probably too old.
Looks like you're using the shader in your object draw calls instead of only when you're rendering the application surface.
Does the demo work?
If Godot supports GLSL ES, then sure, the fragment shader should work fine as long as you hook up all the uniform/varying variables correctly.