To highlight the item in the collectionview when the mouse is hovering it, you can just use the VisualStateManager PointOver state.
<VisualState Name="PointerOver">
<VisualState.Setters>
<Setter Property="BackgroundColor" Value="Red" />
</VisualState.Setters>
</VisualState>
Source: https://learn.microsoft.com/en-us/dotnet/maui/user-interface/visual-states?view=net-maui-9.0