Apparently, no power in Heaven or Earth can make a Dell Windows “mobile workstation” display 4K@60Hz on an external monitor, using any of its ports, cables, connectors, or adapters, despite every piece in the chain assuring me that it can.
Who do I bill for the last half hour?
Bonus points for Windows losing its patience through the process, and not allowing me to resize the graphics options window after some point.
UPDATE: In desperation, I dug around in all my storage, and found the tiny USB-C-to-USB-A/HDMI adapter that came with the laptop. BEHOLD! That one works. I guess my “certified” Anker converter was not, in fact, up to spec.