RPi + LibreELEC SK6812 - Only single color

Hello,
I have a SK6812 strip directly connected to a rpi 3b. I only get a single color (white) working on the strip. I have no boot animation and I am not able to change the color using the color picker tool in hypercon.

Setup:
rpi 3b
SK6812. For testing purposes I only have 8 leds connected

Wiring:
DC 5v > strip '5v'
DC gnd > strip 'gnd'
rpi gnd (pin #9) > DC gnd
rpi SPI (pin #19 or #21) > strip 'Do'

hyperion.config.json:

Code:

    {
        "name"       : "MyHyperionConfig",
        "type"       : "ws2812spi",
        "colorOrder" : "grb"
    },

I use the 'WS281X-SPI' config type because that seems to be the only config type where the leds fire up. I have tried 'WS281X (RPi1, RPi2, RPi3)' with many different config variables but I never got that working on GPIO18 (pin #12).

So: I only get a static white color. I am not able to change it using the color picker and I don't get a boot animation.
What can I do from here?

 

Default pin for SPI is pin 12 unless you also specified the gpio in the config, which your pasted example doesn't have.