Is there a version of Libre Office that works on Google Chrome PCs ?
Good question!
Short answer: No
Longer answer: Maybe eventually…
There was a company that provided an app for ChromeOS that provided an interface to a cloud-hosted build of LO, but they discontinued the service.
Given the design of ChromeOS basically has the user running everything through a browser, one promising avenue might be the experimental support for running in a web browser. Users would either have to have the backend of LibreOffice running on a separate server of their own, or would have to figure out how to get the backend to run on their device (which might be difficult if the OS is quite locked-down for security reasons).
Another route forward would be to just compile and run LO directly on the device. One would probably want to start with the FLOSS version of ChromeOS, ChromiumOS, and see how hard it is to get something built. Of course, at that point, one could just replace the OS with a common distro like Debian that already provides LibreOffice as a package…