Any way to use a standard material for viewport?

[TijuanaKez]

I often still use 'billboard' type objects in scenes, i.e plane with image+alpha texture.
Alphas works fine in the opacity channel for Octane materials, but in the viewport the backgrounds are opaque and black which can make the whole scene black the way I'm using them.
Is there a way to have a standard cinema4D material just for the viewport so the alphas work?

[aoktar]

In settings, we option to activate alpha. It's not on by default because some weirdness