I think you raise an interesting point. I haven’t considered Red Hat Linux, but according to my definition this shouldn’t be Linux then… I still don’t think I feel fully comfortable calling it Linux, because a lot of stuff is watered down. Years ago I used Cloudready, and even though it was based on ChromeOS it used Flathub. I think for me that made a huge difference, because then I could install Steam, LibreOffice, Zoom and Firefox on my ChromiumOS laptop, without having to go through a Linux emulator. I still want to knoe why Google didn’t use this functionality in mainstream ChromeOS.
In the current version of ChromeOS, as far as I know, either you sideload Linux or Google completely controls all app stores. For me that is a fundamental conflict with the promise of freedom and user control that Linux gives - with a simple sudo you can be lord of the world. I think your comment made me realize that that ChromeOS cannot be called not Linux, because it clearly has similarities. But Red Hat doesn’t control your way of getting new apps. For me that is a major difference. Ultimately one could raise a point that MacOS is also Linux, because it uses Darwin - and so I think we need to use different definitions than just a pure “we share same technical basis”.