Another knockoff Neopixel failed in the usual way, after a few days of operation: the first W2812B chip in the string gave off intermittent and random flashes of pure primary colors, the second was dead in the water. Replacing the first chip with Yet Another Knockoff from the same lot restored the tube to good health.
Some oscilloscope probing revealed a pooched serial data output with no active pullup, so the output data rarely exceeded VCC/2 and generally wouldn’t be accepted by the downstream W2812B. Nothing to show for it, as I couldn’t be bothered to upload a scope shot. Maybe next time.
One of the counterfeit FTDI USB-to-serial adapters in another tube base failed after a few weeks of operation, with symptoms ranging from hangs while downloading the Arduino program to readback verify mismatches. Replacing the failed adapter and the knockoff Arduino Pro Mini with a knockoff Arduino Nano (using a CH340 USB interface, presumably not a counterfeit) from a recently arrived envelope restored that tube to good health.
All in all, those knockoff Neopixels have been a constant source of amusement; worth every penny just for the privilege of holding them up for ridicule. The “genuine” FTDI chips weren’t much of a surprise, but I am mildly surprised they work so poorly.