If you have an older OptiPlex, pull the side off and there will/might be a white sticker with a single digit number on it. The number refers to the state of the ME/AMT.
For example, I have an older OptiPlex 780 that has a "3" which means the ME/AMT is completely disabled. I've checked every way I know how and it isn't "visible" at all. Apparently the end user does have some limited ability to change the status, though.
I'll see if I can dig up the info on this.
Edit: Not really what I was looking for but here  is a thread on Dell's support forum that discusses this and how to change the state, etc., by accessing the MEBx on system start (by hitting CTRL-P).
I wonder if this means that it's also possible to disable ME on those machines after purchase (without triggering Boot Guard)?
Dell only offers a single download per firmware version per model (or group of models) to cover all configurations, so presumably it contains multiple images (i.e. AMT-enabled, AMT-disabled, ME-disabled), and the updater just uses ME status or DMI data to determine the correct one.
If that's the case, then surely it should be as simple as manually extracting and flashing the ME-disabled image, right? That's assuming it's actually included in the publicly available updaters, and that all of the images are signed with the same key, of course.
That would be a dream computer.
The 25th Anniversary laptop got close but because it's T470 based so there's only a single, crippled Thunderbolt in there and it's slightly heavier.
I’d rather not have anything to do with Windows, and would appreciate the gesture of a discount for the Windows license (and the money not going to MS).
just kick $10 off my price tag and I'll be happy. If you just sell me an empty shell (no disk or ram) which I'll be over charged for I'll be even happier.