The GameCube hardware was manufactured in three regional variants, each with a matching DAC (suitable for standard definition modes only) and bootrom:
(the "digital video" connector completely bypasses the DAC, hence the high price of devices using it which must provide their own)
The Japanese and American consoles output NTSC video in composite and S-Video, using the connector that has been customary since the Super Nintendo. 50 Hz modes output as NTSC50?
They are otherwise the same except for an internal jumper, which can be brought out (and indeed has been officially done for developer models).
The European GC outputs video only in PAL (4.43) composite (SNES/N64 compatible connector) and RGB (different but more because of lack of effort and cost-cutting in those previous consoles). 60 Hz modes output as PAL60.
They don't have a semi-official region mod but do have a multilingual IPL.
The Brazilian system is based on the American model, but with a different ROM which may not support dual region.
Its DAC is software switchable between NTSC and "PAL-M", however no PAL-M software except for the bootrom itself was ever released (commercially; Swiss supports it fine!)