Hello,
I recently bought the Unicorn LED display for the Raspberry Pico and like you I was rather disappointed to find only c code and python support.
Fortunately I have created libraries before to support displays, so based on the Pimoroni example I have created one here:
This is not available from the Arduino IDE library manager yet but I will suggest it is included. The library uses the Adafruit_GFX support library which is well documented. I have included one example to get started but will add more in future.
Hope this helps you, but it may be a bit late for your project!
You will need to use the Earle Philhower RP2040 board support package as the PIO is used to drive the display. That is available via the Arduino board manager.