If you're specifically looking for a product key because you're trying to install Linuxfx 11 from a source that requires it, I recommend:
: Activating a key unlocks features such as native support for Linuxfx 11 Product Key
It is important to distinguish between the kernel (Linux) and the user experience (the UI). Linuxfx creates a Windows aesthetic, but under the hood, it is Linux. If you're specifically looking for a product key
: If you are looking for older ISO files, they are sometimes hosted on the Internet Archive . Finding an Existing Key but under the hood