How do I control multiple object's opacity using a custom attribute?

[HoltHunter]

I am creating an animation that requires me to animate the opacity of multiple objects. What I don't want to have to do is go into the material of each individual object and animate the opacity from the shader editor. The main reason I don't want to do this, is that it would require applying a unique material to each object. In the scene, all of the objects have the same material. I feel like a much more elegant solution would be to somehow control the opacity of the material using a custom attribute on the object. I've attempted this and used wire parameters to link the custom attribute on the object to the opacity attribute on the material, but this changes the opacity for all of my objects at once. If possible, I would like to keep a single, shared material applied to all of the objects, but control the opacity individually. I have seen the User Data shaders, but I can't figure out how to use them. Is there a way forward using them?

[CAMedeck]

You can control the visibility of individual objects, and animate it pretty easily.  Right click with an object selected and choose Object Properties.  You'll see a visibility parameter there.  You can also access that value by adding a Visibility Track in Track View.  If you have several objects that will all have the same opacity changes, you should be able to link them to a common object and they'll inherit their visibility from it.