Here's an HN thread [0] from a few years ago regarding "advertising" in the MOTD, specifically, and Ubuntu's "dynamic" MOTD, generally. (I'm not sure if all of the hardware/system details were being sent back then, though.)
The relevant "snippets" responsible for this behavior live in their own directory, /etc/update-motd.d/, if memory serves. That may not be exactly right -- perhaps unsuprisingly, I don't have an Ubuntu box handy -- but it should at least be close enough to help you find the actual directory.
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[0]: https://news.ycombinator.com/item?id=14662088