I recently put Debian on an old 13" Asus Chromebook. It was surprisingly easy! I don't remember doing much other than removing a screw and installing a UEFI firmware on it. Everything worked out of the box.
It works pretty well too, as long as you temper your expectations around 4GB of RAM and aren't expecting to watch YouTube on it. (Older machines and phones are just not at all happy about 60fps videos.)
IME it's generally trivial for x86 Chromebooks, but still hit-and-miss for ARM.
The lowest spec machine I have been able to get 60fps 720p video out of Youtube is a 2nd Gen i5 2.4Ghz. Anything lower and the frames start dropping.
It is funny that during that time period, Intel's media decoders got significantly faster in a very short period of time. My 4th gen 2Ghz i5 decodes video better than my 2nd Gen 3.8Ghz i7.