Ionic development for iOS in a windows or linux environment is it possible?

This is not possible because MacOS and XCode features such as the iOS SDK environment are required to compile iOS applications.

The closest options would be:

• Cloud
  Cloud Compiler services are apps. In this case, any operating system can be used because the compilation work is determined by the computers of the company that provides the service. Here you "lose" the privacy and even security of the project, as it is giving "tray" codes to a third party. But it is not a bad option. Each should calculate their own risks. However, this is another matter not relevant to the questioner.

• Virtualization
  Install MacOS through virtualized environment (VirtualBox, VMWare, etc).
  It is usually a complicated task and will hardly have a satisfactory result. Most of the times it does not pay off but it's as simple and close to what you need.

• Hackintosh
  Make modifications in the hardware configurations of a PC to be able to install a MacOS. In this case it ceases to be Windows or Linux, which would escape its objective. The only "advantage" is not having to buy a Mac.
  It is also a very complicated task and most of the time is ineffective. Of course, you should not do this in a corporate environment.

Personal opinion, do not be fooled by gambiarras. At first they may bring some result (well pig), but will not be able to keep it safe and stable. * referring to hachintosh and virtualization

The "secret" of these "hybrid" development platforms is actually a big hit. It's all based on HTML / JavaScript that runs under a "webView" class of the target operating system (Android / iOS).
Basically a browser window is opened within the app. Summarizing roughly, the final app is just a "hole" on the screen that calls the browser's default operating system and captures JavaScript events. These JavaScript events are captured by the device's native capabilities, so access to certain native features is possible.