[Matt Devo]

Thanks for the further input, Matt Devo. Another thing I've noted: if I'm understanding correctly what I'm seeing at the tty, I also have the option of just enabling USB boot, thereby obviating the need to run the script, partition the drive, etc--correct? In other words, I could just run LE from USB that way, it seems. If so, what are the pro's/cons of setting up dual boot ChromeOS/LE versus just leaving ChromeOS and running LE from USB? Still deciding which course of action I'll pursue.

regardless of whether you want to run LE from the internal SSD or USB, you need to use the EZ Setup script to update the legacy BIOS, as this updates the RW_LEGACY firmware and sets the dev_boot_legacy flag to enable the use of CTRL+L. "Enabling USB boot" is something that blogs say when they don't know anything about how Chromebooks/boxes actually boot. You're using Legacy Boot Mode either way.