Lance Uno and Telerik app.xaml

App.xaml

<Application
    x:Class="UnoTester.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:UnoTester"
    xmlns:controls="using:Telerik.UI.Xaml.Controls">

    <Application.Resources>
        <ResourceDictionary>

            <!-- Note: This App.xaml is a workaround to load the resources, it is supposed to load without this -->

            <controls:UserThemeResources x:Key="themeResourceInitializer"/>

            <ResourceDictionary.ThemeDictionaries>
                <ResourceDictionary x:Key="Default">
                    <ResourceDictionary.MergedDictionaries>
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Controls.Data.UWP/Themes/ThemeResourcesDark.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Chart.UWP/Themes/ThemeResourcesDark.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.DataVisualization.UWP/Themes/ThemeResourcesDark.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Grid.UWP/Themes/ThemeResourcesDark.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Input.UWP/Themes/ThemeResourcesDark.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Primitives.UWP/Themes/ThemeResourcesDark.xaml" />
                    </ResourceDictionary.MergedDictionaries>
                </ResourceDictionary>
                <ResourceDictionary x:Key="Light">
                    <ResourceDictionary.MergedDictionaries>
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Controls.Data.UWP/Themes/ThemeResourcesLight.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Chart.UWP/Themes/ThemeResourcesLight.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.DataVisualization.UWP/Themes/ThemeResourcesLight.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Grid.UWP/Themes/ThemeResourcesLight.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Input.UWP/Themes/ThemeResourcesLight.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Primitives.UWP/Themes/ThemeResourcesLight.xaml" />
                    </ResourceDictionary.MergedDictionaries>
                </ResourceDictionary>
                <ResourceDictionary x:Key="HighContrast">
                    <ResourceDictionary.MergedDictionaries>
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Controls.Data.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Chart.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.DataVisualization.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Grid.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Input.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                        <ResourceDictionary Source="ms-appx:///Telerik.UI.Xaml.Primitives.UWP/Themes/ThemeResourcesHighContrast.xaml" />
                    </ResourceDictionary.MergedDictionaries>
                </ResourceDictionary>
            </ResourceDictionary.ThemeDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>