You are wrong on everything. Google gives 10 years of updates, once the support lifetime ends you can put flex on it, linux, but chromeos keeps working, you just stop getting updates. Mostly that is because a 10 year old device is pretty slow, you'll want to faster device.
I have one 10 year old mac laptop, all I can do it boot it and wait minutes for the login panel to show. Actually I should get rid of that as ewaste.
I'm at seven years and counting with my OG Pixelbook and still getting regular updates. Although it is currently serving as a dedicated Home Assistant dashboard using a fantastic app called WallPanel (via the Android compatibility layer on ChromeOS).
Once Google EoL your device (within a year or two lol) it’s as good as paperweight.