While both technically wrong and true of every computer, many Chromebooks can run non-Googled Linux distros and far outlive their support term… $50 might get you a very nice, lightweight, and portable “netbook” on the used market that you can use another 5 years for basic tasks.
ChromeOS, outside of being Googled, is quite capable (crostini is really nice), well secured (minus Google privacy concerns), and generally a nice user experience. You can even run Firefox and avoid browsing with Chrome.
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).