I tried your code, but I don't see the item in the footer.
<Shell.ItemTemplate>
<DataTemplate>
<Frame CornerRadius="5" Padding="0">
<Grid ColumnDefinitions="0.2*,0.8*" VerticalOptions="FillAndExpand" BackgroundColor="LightBlue">
<Image Source="{Binding FlyoutIcon}"
Margin="5"
HeightRequest="45" />
<Label Grid.Column="1"
Text="{Binding Title}"
FontAttributes="Italic"
VerticalTextAlignment="Center" />
</Grid>
</Frame>
</DataTemplate>
</Shell.ItemTemplate>
<controls:FlyoutItemIconFont Title="Home" IconGlyph="{StaticResource IconHome}">
<ShellContent Route="HomePage" ContentTemplate="{DataTemplate local:HomePage}" />
</controls:FlyoutItemIconFont>
<Shell.FlyoutFooter>
<controls:FlyoutItemIconFont Title="Instellingen" IconGlyph="{StaticResource IconInstellingen}">
<ShellContent Route="SettingsPage" ContentTemplate="{DataTemplate local:SettingsPage}" />
</controls:FlyoutItemIconFont>
</Shell.FlyoutFooter>
</Shell>