Chrome OS Flex is Google’s official answer to your search. It is a free, x64-only operating system designed to run on old PCs and Macs. It looks exactly like Chrome OS, supports automatic updates from Google, and can be managed by enterprise IT.

Once you've booted from the USB drive or virtual machine, you'll be greeted with the Chrome OS x64 installer. Follow the on-screen instructions to:

The Ultimate Guide to ChromeOS x64 ISO: Downloads, Installation, and Alternatives