How long does it take a dog to digest food

If it is going to digest, about the same time as other foods - approximately 24 hours - perhaps a little longer. I can only speak from experience - watching my dogs poop for signs that they’ve digested bones. The poop becomes whitish, or very light, from the large amounts of calcium.
I don’t have a scientific study to validate this, but from my experience, cooked bones and raw bones digest at similar rates.
On a side note, bones do present some dangers, both cooked and raw, but raw are generally somewhat safer, as they are more flexible. Cooking makes bones more rigid, and they splinter more readily.
If the bone is not going to digest, dogs will often throw them up. I do see this occasionally. On the other hand, although people speak of the danger of blocked and/or perforated bowels, I’ve never seen such. I’m sure it happens - I believe it when vets tell me they’ve seen it. But I don’t think it is common. I’ve known way too many dogs who’ve gone their whole lives chewing bones, and never had an issue. Even worse is an example from a cousin of mine, who had multiple dachsunds. They allowed their dogs to eat their discarded fried chicken bones. I was young at the time, and based on what I’d been told, these dogs were automatic deaders. Except, they weren’t. They lived full and long lives, sans problems. (Note: in response to comments, I am NOT in favor of ever giving dogs cooked chicken bones. They increase the risk level for having an adverse outcome - like perforated intestines, etc. So no, not a good idea. However, the example does point out that getting all dramatically excited, e.g. “Oh! You should NEVER EVER . . .”, is a bit of an over-reaction. If a dog eats a cooked chicken bone, it is not an automatic death sentence.)