You can even install linux on Chromebooks, and ChromeOS has upstreamed / opensource many of their codes.

In other perspective, ChromeOS supports running Linux apps w/ GUI without much differences. You just open your terminal, type `apt install XXX`, then `XXX` should work out-of-the box.

I don't see any reasons that ChromeOS is less open then macOS

Any? Crostini is neat and all, but it's a VM running inside of ChromeOS, so it's restricted in what it can do.