So, I do not have a
dead hard drive on the media computer. Rather, it turns out I held down the power button for too long.
I'm very lucky to have figured this out. I happened to see this
little comment:
What happened was that I long-pressed power button for my Dell laptop for like 30s and then this BIOS config was reset to RAID somehow.
Sure enough,
this is a real thing.
The Real-Time Clock (RTC) reset function allows you or a Dell service technician to recover a Dell Latitude, Inspiron, Precision, Vostro, Alienware, or XPS laptop from a no power, no POST, or no video issue.
The RTC reset resets the BIOS to factory default settings, reset the computer date and time, and unprovision Intel vPro
So, it reset the BIOS, which apparently turns no RAID by default (even though I have a single hard drive), and Ubuntu then cannot find any hard drives; no `/dev/sda1`.
Absolutely insane design decision! There's no beep or anything to let you know something's happened.
That computer is working again, but its days are probably numbered. It lost Bluetooth and doesn't recognize the sound card. (Though there's some chance it's an Ubuntu 24 update issue. I've since turned off non-security automatic updates so that I don't have to worry about this possibility.)