Hello zanfafx,
I think the error is pretty simple to fix:
Shader Forge(SF) is used in the tutorial and you are using Amplify Shader Editor(ASE). These have some bigger and smaller differences, so you have to keep an eye out when transferring shaders from one to another.
What’s happening here is, that in ASE, the bundled output is “RGBA” and not “RGB” like in SF. Therefore, you are multiplying alpha again on top of the alpha.
Also, it should not be needed to change anything in blend options on the left.