I try to run my spare Raspberry PI 3 Model B+ with the most recent version of Alpine Linux (3.9.0). After I plugged everything in, HDMI, keyboard, LAN, SD Card and power, I don't get any reaction. After trying to select the input on my screen I get no signal and it searches for other signals. It seems like no HDMI signal is send, and only the red power LED is on. The activity LED stays off and it doesn't matter how long I keep it connected to the power it doesn't happen anything.
I get the same behavior if I connect the PI to the offical Raspberry PI touchscreen. I tried several suggestions from the forums but they didn't work.
The hardware is ok, it works with Raspbian.
Edit: Here are the links I tried: