During my work at Semihalf, together with Igor Jankiewicz, we designed the Semihalfino evaluation board, which is based on the RP2040 MCU (this project was historically the first).
Due to the long development time, a side effect was the Carduino Pi project (as a second evaluation board based on common schematics and PCB layout), because I wanted to verify the whole concept of the RP2040 in the Arduino format.
The third project (Polanduino) was another modification as I noticed that so far no one has designed a classic Arduino board for the RP2040.

Carduino Pi:
https://hackaday.io/project/188770-carduino-pi

Polanduino:
https://hackaday.io/project/188769-polanduino

Semihalfino:
Unfortunately this project has not been officially published so far, so I cannot share its source files.