RPi3 with only HDMI attached never shows subiquity

The display has carrier and sync.

I see the bootloader begin and load initram and kernel.

Kernel starts. I see four fruit!

Then, silence. No lines. No blinking cursor.

Heartbeat LED blinks. Keyboard press of numlock or capslock toggles its indicator. I can't switch VTs, judging by the fruit remaining and lock lights remaining constant.

If I edit cmdline.txt and add "console=tty0" after the serial console, no change. Blinking heartbeat. Numlock toggles. No VT switch.

If I edit cmdline.txt so the only "console=" line is tty0, then I get

at second 30, kernel starts booting. Four raspberries at the top.

at second 36, starts resizing disk, which takes three seconds.

at second 37, starts systemd. Heartbeat LED STOPS BLINKING.

at second 48, turns on networking.

at second 54, black screen with blinking cursor at top left.

at second 64, press-enter-to-configure.

I think the absence of a console device makes the step right around resizing and starting systemd to hang.