Please include the target versions that you're using. I assume from "Drawable" that you're targeting Xamarin.Android native UI and not iOS or Forms, but it's clearer if you're explicit about that.
Xamarin.Android is a light wrapper around the Android API, so you have access to and the same capabilities as a native Android app. Android doesn't provide a TextDrawable, so the common pattern is to create a custom TextDrawable by inheriting from Drawable and handling the Draw method to call Canvas.DrawText.
There is an example of handling OnDraw to draw with a Canvas in the Xamarin Android Graphics and Animation documentation.
There are a number of native Android implementations you can look at that should be easy to port to C#, as well as at least one C# implementation, though I don't know if it's current enough to work as is.