Since I couldn't find how to control it, here's my code how I did it. They probably focus on their python stuff more than on the Arduino IDE, which makes sense and all in all the Trinket still works with the Arduino IDE, so hurray :) You need to install the Adafruit_DotStar library, best done with the library installer. I had to change the datapin and clockpin, easy to find on the pinout site (https://learn.adafruit.com/adafruit-trinket-m0-circuitpython-arduino/pinouts. The other change I had to make was the configuration definition to BGR, RGB backwards. Now that I was able to do that, I found this https://forums.adafruit.com/viewtopic.php?f=25&t=124501&sid=21195cd2275abc7ba8a32912d47cff6f :D

// Simple strand test for Adafruit Dot Star RGB LED strip.
// This is a basic diagnostic tool, NOT a graphics demo...helps confirm
// correct wiring and tests each pixel's ability to display red, green
// and blue and to forward data down the line.  By limiting the number
// and color of LEDs, it's reasonably safe to power a couple meters off
// the Arduino's 5V pin.  DON'T try that with other code!

#include <Adafruit_DotStar.h>
// Because conditional #includes don't work w/Arduino sketches...
#include <SPI.h>         // COMMENT OUT THIS LINE FOR GEMMA OR TRINKET
//#include <avr/power.h> // ENABLE THIS LINE FOR GEMMA OR TRINKET

#define NUMPIXELS 1 // Number of LEDs in strip

// Here's how to control the LEDs from any two pins:
#define DATAPIN   7
#define CLOCKPIN   8

Adafruit_DotStar strip = Adafruit_DotStar(
  NUMPIXELS, DATAPIN, CLOCKPIN, DOTSTAR_BGR);

// The last parameter is optional -- this is the color data order of the
// DotStar strip, which has changed over time in different production runs.
// Your code just uses R,G,B colors, the library then reassigns as needed.
// Default is DOTSTAR_BRG, so change this if you have an earlier strip.

// Hardware SPI is a little faster, but must be wired to specific pins
// (Arduino Uno = pin 11 for data, 13 for clock, other boards are different).
//Adafruit_DotStar strip = Adafruit_DotStar(NUMPIXELS, DOTSTAR_BRG);

void setup() {
  strip.begin(); // Initialize pins for output
  strip.show();  // Turn all LEDs off ASAP
}

void loop() {
  strip.setPixelColor(0, 0xFF0000); // red
  strip.show();
  delay(1000);

  strip.setPixelColor(0, 0x00FF00); // green
  strip.show();
  delay(1000);

  strip.setPixelColor(0, 0x0000FF); // blue
  strip.show();
  delay(1000);
}