Preconfigured servers do not feature KVM or IPMI. You can OS reload your own server from the web portal. You can also boot to a "rescue mode" which does not overwrite the hard drive.
You may attempt to install any non-Windows OS through a temporary KVM.
If you'd like an alternative OS not listed on checkout, when you complete your order online select “none” for the operating system and then in the comments section of the order form write “setup KVM and I will install OS myself”.