Arduino Nano Every & 27 WS2812B LEDs not quite working as expected

[anon57585045]

@Chrotesque

So what you're suggesting is that the random colors & flickering can be solved with a separate power supply for the LEDs alone?
What about the resistor in between Arduino data pin and LEDs, is that something to consider? I've read mixed things on this topic.

Yes, and yes. The resistor is mainly important with cable lengths longer than a few cm.

It's cool if you run both Arduino and LEDs from the same 5V supply, just not the onboard one.