As I recall, the conclusion was that something was missing on the Linux implementation under ChromeOS, which means snapd doesn’t work there. I don’t know that anyone on the snapd team has a pixelbook so not sure we can test and debug this. So your help is very much appreciated.
I note you tried to install squashfuse from the archive and it wasn’t available. That’s kinda a blocker, if we can’t rely on a typical piece of the puzzle to be there. Looks like the Linux implementation on ChromeOS has a limited set of packages, which unfortunately is a bug upstream in the ChromeOS Linux implementation, in my opinion.