There is? Does it exist on iOS? If so, how do you get to it?

On Android it's Menu -> Help & Settings -> App Settings -> Links open externally.

It's more buried than maybe it needs to be (to be fair there are a lot of obscure settings in this monster of an app), but basically findable.

Rather than crashing the thing, it's probably more productive for web developers with serious compatibility issues just to detect it and tell users how to find the setting.

On Android, if you install a new application that can handle links, Android will ask you the next time you click on a link how you want to handle it.

On Android if you are not a heavy FB user you should be using something like Metal or Swipe.

By convention, many apps on iOS detect whether Chrome is installed. If you click on a link, the application pops up a dialog asking whether you prefer Safari or Chrome and remember the choice. Sadly, this is done completely at the application layer.

Where is this setting?

On Android: App Settings -> Links open externally