How do I fade a whole scene? I have a scene that I want to fade to complete transparency on the outside. The blue object in the picture (continues in the larger red/white object) should gradually no longer be visible from the beginning of the red towards the white. If possible, the whole thing should also work in eevee.
You can do this using shader node too(Procedurally)
Follow this node group:

Value node gives the fade effect. Play with the values to get the desired effect.
Result:

P.S. Make sure you join both the objects
P.P.S If you wanna change the axis on which the fading occurs, change the value of last greater than node with Y or Z output from separate XYZ node
BLEND FILE: https://pasteall.org/blend/e1e9617c0bed4c18b372d759462ffb94