Welcome to the SeeMeCNC Community

Just today, my display went dark while warming up for a print. The power supply still fires up, fan runs, but there are no LEDs on the RAMBo that are lighting up.

My cursory inspection shows no loose wires or connectors, no obvious damaged or burnt-out CCA components.

Did my RAMBo give up the ghost? Are there some other recommended troubleshooting steps to take?

Sounds like a short somewhere may have taken out one or more of the microfuses. There are a pair of surface mount fuse holders on the board that hold tiny fuses. Take each out, and test it for continuity. Then test each output for a short circuit, with the power off.

Good intuition - the upper fuse, F3, measures as open.

While I wait for a replacement part, I'll troubleshoot the wiring out to the fans and hotend heater for shorts / loose connections.

[edit] The short was found on the hotend heater circuit. I had connectorized the lines for easier hotend removal and servicing -- solder-cups of the connectors had contacted a metal fastener near the hotend. The solder-cups are all covered up with electrical tape now.

May I suggest you buy either some heatshrink, and re-terminate, or use some heat shrink tape? Electrical tape is usually not well formulated for use on moving cables, and may unwrap and put you in the same spot.