Running PowerShell to install MSIX from .NET MAUI

var prefix = Path.Combine(FileSystem.Current.AppDataDirectory, "Downloads");
var filePath = Path.Combine(prefix, "myappname.msix"); // <-- Confirmed to exist, not the issue

var scriptContents = new StringBuilder();
scriptContents.AppendLine("Param($FilePath, $ForceShutdown)");
scriptContents.AppendLine("Add-AppxPackage $FilePath $ForceShutdown");

var scriptParameters = new Dictionary<string, object>()
{
    { "FilePath", filePath },
    { "ForceShutdown", "-ForceApplicationShutdown" } // <-- Or -DeferRegistrationWhenPackagesAreInUse
};

using PowerShell ps = PowerShell.Create();
ps.AddScript(scriptContents.ToString());
ps.AddParameters(scriptParameters);
await ps.InvokeAsync().ConfigureAwait(false);