I have written drivers for Pimoroni's Inky Frames (based on Raspberry Pi Pico W) in Nim, but I don't own an Inky Impression. The code should be pretty similar once it hits the SPI bus.
I have planned to write GPIO/SPI/I2C "drivers" in Nim that interfaces with the Linux drivers. So far I have made a wrapper for libgpiod. https://github.com/daniel-j/nim-gpiod