Been discussed on here before. Currently it is not possible IF you have a lock code enabled. This has to do with Apples security and nothing to do with app developers. If you dont have any security enabled on your phone then you can use 3rd party keyboard.
Are you sure about this?
So i amassuming apple prefers their own keyboard anytime passcodes are being entered in even in apps and safari it switches to apple keyboard
I get, but that doesn't mean I'm not sad about it.