David, do you often, or ever, even, have a situation indoors where you use available light?

Sure. I assume you mean available daylight, not a night scene lit by practical lamps, which is a form of lighting.

If the scene is short and I don't have to worry about light continuity problems from taking several hours to cover the scene, and the natural light looks good and I have enough exposure, sure, I'll take advantage of it.

And in terms of night interiors, yes, I've lit scenes with just practical lamps.
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David Mullen, ASC