MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:ContextAndType"
             x:Class="ContextAndType.MainPage"
             x:DataType="local:ParentViewModel">
    <ContentPage.BindingContext>
        <local:ParentViewModel />
    </ContentPage.BindingContext>

    <VerticalStackLayout>
        <Label Text="{Binding Text}" />
        <Label BindingContext="{Binding Child, Source={RelativeSource AncestorType={x:Type local:ParentViewModel}}}"
               Text="{Binding Text2}" x:DataType="local:ChildViewModel" />
    </VerticalStackLayout>

</ContentPage>