How relevant are these technologies?

Question

QML

Now I practice in web development, but sometimes I look towards other technologies, namely the creation of applications in c# or java. I heard that when building an interface, 2 approaches are used: using markup languages ​​(xml, qml, xaml) or using program code and a graphic library (like PyQt5 in python). And here is the first question: are xml-like languages ​​​​relevant now for creating interfaces, and how often and where are they used?

Answer 1

In Xamarin it is relevant, in Android Axml.
Html5, by the way, is also xml, well, you get the idea, yes.
codeigniter is like PHP ?
Do not know