Get a used T- or X-series Lenovo Thinkpad with Intel graphics from Staples or Ebay or thinkpaddepot.com or outlet.lenovo.com. I have a T420s and an X220i that run Ubuntu, Slackware and OpenBSD. I'm unsure how well Nvidia chipsets are supported by Ubuntu, and I know they're not supported at all by OpenBSD.
One caveat: some OpenBSD firmware isn't included in the standard installation media, so one needs either to do the install while connected to the net via Ethernet, or download the firmware from firmware.openbsd.org onto media and run fw_update after installation.
