Console Variations has gotten hold on a prototype of the Nintendo GameCube, called Nintendo Dolphin and posted one picture.
Dolphin was the original name Nintendo used for the GameCube until the finalization of the name. However, it was closer to the GameCube that was released in 2000 in design rather than the original NPDP-GDEV prototype that first resurfaced in the 2014.
While it shares the GameCube’s trademark purple color, the power button was on the upper right side of the console instead of the upper left side of the Dolphin.
Console Variations did not explain how they acquired the prototype, noting that they are not allowed to share more pictures due to the console being still proprietary.
The only other possible picture is from a picture from site Raregamingdump alongside the StarFox Adventures. It is possible that it might be the same prototype Dolphin, but this is still unclear.