When using a TemplateCell, selection does not fire on Android. 

Reproducible (use SelectionChanged and SelectionUnit="Row"):

<telerikGrid:RadDataGrid.Columns>
    <telerikGrid:DataGridTemplateColumn HeaderText="Key">
        <telerikGrid:DataGridTemplateColumn.CellContentTemplate>
            <DataTemplate>
                <Grid Padding="0,5">
                    <Label Text="{Binding Key}"
                           VerticalOptions="Center"
                           TextColor="Black" />
                </Grid>
            </DataTemplate>
        </telerikGrid:DataGridTemplateColumn.CellContentTemplate>
    </telerikGrid:DataGridTemplateColumn>
</telerikGrid:RadDataGrid.Columns>


WORKAROUND

Set the DataTemplate content's InputTransparent="True" so that input event is passed through the template to the DataGrid:

<DataTemplate>
    <Grid InputTransparent="True">
        ...
    </Grid>
</DataTemplate>