Well, it seems that there have been several crashes over the last few years where no on-site footage surfaced... whether there's any of this one or not.

Footage existing and footage being released to the public are two different things.

I understand there is a public Voyeur interest in seeing crashes, but how does releasing footage of accidents aid investigation or safety outcomes?

It can aid pilots, for one thing. I watch air-safety/accident-analysis videos all the time. They are often extremely informative and promote a safety-oriented mindset and the refreshment of one's commitment to procedure.

I also read scuba-diving accident reports. They reinforce best practices that I also explain to others in the context of what I've seen in said reports over and over.

Watching the various yt vids with pilots etc, I am considerably less anxious about flying.

Also a good point!

Considering how much effort it takes the NTSB to reconstruct the chain of events from the crash site and flight data recorder, any high-resolution video could be very valuable. In particular I think all airliners should have 4K "dashcams" considering how inexpensive the technology now is.

Crashes aside, a high-res Tower view would also make a great live webcam for enthusiasts to watch while listening to LiveATC.

A view just out the front of the plane wouldn't do much to help crash investigations and one of the big reasons they don't is you have to make a large enough storage resilient enough it can reasonably survive a crash. Most crashes are no where near this gentle.

Far more useful would be an interior cockpit view showing the crew and the actions they were taking but a lot of that is recorded to the FDR on newer planes too.

True. A better external placement would be a wide angle tail-mounted camera that can film the entire aircraft from the rear. Some airlines (e.g. Emirates) already have this live view available on the infotainment.