Xcode is used to install / create simulators. Xcode-> Window -> Devices & Simulators. in vscode you pick the platform from the bottom menu bar (left of C#{})
you should just build with the dotnet cli to see that all is installed and configured:
https://learn.microsoft.com/en-us/dotnet/maui/ios/cli?view=net-maui-8.0
vscode maui article:
https://www.telerik.com/blogs/beyond-basics-getting-started-net-maui-extension-visual-studio-code