Today’s mobile apps are rarely created as text-only. Most of them needs at least in-app icons for toolbars. In many cases you can find graphics for mobile platforms as ready to use resources on the Internet, i.
Modern mobile apps are rarely developed as offline-only. They typically communicate with backend services that feed them with data, keeps in sync with their web equivalents or allows for various external integrations.
Standard Xamarin.Forms Xamarin.Forms.Editor control offers edit capabilities similar to Entry but for multiline text. Unfortunately unlike Entry it doesn’t support displaying placeholder text out of the box.