to build an iPhone executable you need a Mac and an apple dev account to create a signing certificate. Visual Studio will remote to your Mac to do the build and signing. see pairing a Mac to visual studio 2022:
https://learn.microsoft.com/en-us/dotnet/maui/ios/pair-to-mac
note: you need to manually install Xcode and accept the license on the Mac. I believe you need to use Visual Studio preview and .net 8 to use the current Xcode version 15.