How do you remove Enterprise Enrollment?

Can't be done, it's tied to the S/N of the Chromebook and the MDM is provisioned at the hardware level somewhat persistently. Power washing it temporarily clears it, but it always comes back due to the S/N tie. This is the same reason you can't remove Microsoft Intune easily; it ties to the S/N or UUID so if you buy a used machine from a company who doesn't remove it, you're screwed without a replacement system board. I know how to bypass the MDM on Intune, but I don't do it because the machine is a almost always a ticking time bomb waiting to fail at any time, worse when it's Intune with JAMF and it locks up when it's put online. They're not something one can save easily without a whole new system board to give it a new identity :-(.

Anyway, the machine will usually provide details (or a cue, like a Pasco County Gsuite account) as to who owned it - be it a school district or company as there's usually something there like a company logo. See this W11 EliteBook for what to (sort of) look for:

Sometimes you can call and get them to work with you (bonus points if you have credentials that work in your favor, and the ability to talk them into giving you information on who to talk to) but most of the time you're screwed short of a new board :-(. With high-end laptops that just left warranty, finding a unit that is garbage cosmetically but has a working board (and sometimes 1-2+ years of warranty left) and come out ahead. Not so much with Chromebooks because they were cheap when new, and depreciate accordingly.