Just need the power LED to know it's on, hard drive and keyboard LEDs to know it's doing something and POST beep codes to know why it's broken.

dmesg is always fun though nowadays it requires root or sudo

other hot utilities that start with ls: lsblk lspci lsusb lsmod

or you can just cat random /proc or /sys files

I suppose if you want to read some logs and are running systemd you can journalctl

honorary mentions to hdparm, smartmontools, lm-sensors

There's also dmidecode command that can parse BIOS info in shell it's useful