The steak sandwich is available on some flights. It is by no means a consistent starter on the menu. And yes, it is considered a snack (available upon request) rather than a main course. From what I have heard and read, it is more likely to be found on flights departing from Australia rather than flights to Australia, but there are always exceptions to the rule.

But if the steak sandwich is not offered on your flight, there will be a hot snack of some description on the menu.