Do we need AdwValueObject?
GTK4 has GtkStringList, which is a lot easier to use than AdwValueObject+GListStore if you have strings. Additionally, GtkDropDown and AdwComboRow special case th GtkStringList and don't require setting an expression to display their items.
Meanwhile, while AdwValueObject is more generic as it works with any GValue, the API strongly looks like "You're supposed to use this with strings" with all the string-oriented helpers, and you have to deal with raw GValues to use any other type.
So, should we remove it and tell people to use GtkStringList instead?