Anyway, now that I know this I’m going to look out for second hand chrome books. Think I could run a Plex server on one?

You can refer to https://mrchromebox.tech/ for a listing of what chromebooks that firmware can be flashed on to (refer to Supported Devices on the left). Chromebooks ship with a modified BIOS that will only work with the Chrome OS that installed on those devices. Their BIOS/firmware is also in read only mode but that can be disabled usually by removing a screw somewhere on the motherboard. After that, you have to flash that alternative firmware over so that the computer can have a BIOS that is compatible with other operating systems (consequently making the computer unable to run Chrome OS).

The FAQ (linked below) mentions that there is a “handy spreadsheet” compatibility list as well. Notably, some Chromebooks are not quite compatible with Linux and show this by literally frying their speakers (supposedly) if you try to use Linux on them… so you may have to be selective in what you purchase.

https://mrchromebox.tech/#faq

AI coming up with sayings of that type is something already being done ( https://inspirobot.me/ ). Youtube reaction videos exist referring to that site (like “Ai Generates Hilarious Motivational Posters” by jacksepticeye).