Hi,
This took me a day to figure out 😞
It seems with the latest version of your Runtime (<PackageReference Include="Esri.ArcGISRuntime.Maui" Version="200.1.0" />) and the latest Visual Studio 2022 Version (Enterprise v17.5.5, .NET MAUI to 7.0.81 (SR4)) maps are not shown anymore.
I've reproduced this on an emulator an two real world devices.
I've created a simple/default .NET MAUI app for your convenience (see zip attached).
The core issue is in the xaml:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
x:Class="ArcGISTry1.MainPage"
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:esriUI="clr-namespace:Esri.ArcGISRuntime.Maui;assembly=Esri.ArcGISRuntime.Maui">
<!-- With "*, Auto" no map is displayed!
Only this works, but is layout-wise not what I want: <Grid ColumnDefinitions="*, *" RowDefinitions="*, *">
-->
<Grid ColumnDefinitions="*, Auto" RowDefinitions="*, Auto">
<esriUI:MapView
x:Name="MyMapView"
Grid.Row="0"
Grid.RowSpan="2"
Grid.Column="0"
Grid.ColumnSpan="2" />
<Button
Grid.Row="1"
Grid.Column="1"
Text="..." />
</Grid>
</ContentPage>
If I put the MapView into a Grid with Auto-Columns/Rows the page stays empty:

If I use just Star-Columns/Rows everything works fine:

Please investigate as I need this to work asap for a upcoming release