brent
I'm glad you finally got a copy. I used Solus Plasma as the example in that document, because I've recently created a Plasma VM, and I know that our .ISO file works. But if you'd rather have a Windows VM, feel free to follow the same instructions with a Windows 10 .ISO file you can download for free from Microsoft.
And if you're really interested in creating a Windows 11 VM, that's a possibility, too. Creating it requires some extra steps, and you need to hack the Windows registry to add some new keys, but it's not very hard. I can let you know how to do that, but I just wouldn't recommend it for your first VM.
To try out other Linux distros, I believe you can follow the same steps in the tutorial, but just substitute the .ISO file you downloaded from their site. I haven't distro-hopped since I found Solus, but I don't remember anything special from back when I created a lot of those VMs.