Gamecube console to MacBook

The only reliable way that I'm aware of is using a capture card connected via USB. I say only reliable because you might otherwise experience latency that makes gameplay problematic with any other method I've heard of.

I used to do this with an Elgato HD60 and my Nintendo Switch to livestream Super Smash Ultimate, or to play on my MacBook Pro when convenient. It was super smooth all around. Hardly any latency to speak of.

With a Gamecube, I'd imagine you would need an AV/Composite to HDMI converter, as most good quality capture cards typically only have HDMI these days.

Good luck!

A "capture card" is what you're looking for when it comes to HDMI to USB. It's an audio / video capture hardware device that's needed to be recognized by software on your computer to get an audio / video feed. Most "capture card" software is free, it's finding a reliable unit that's most important.

I'd start by doing some research on which brands are most used, most reliable, etc. Make sure the specifications suit your needs. Ask yourself if you care about HD upscaling and high bitrate audio, or if it's not that big of a deal since you're primarily using a GameCube. This might change if you plan on streaming down the road. In my opinion, the most important thing in your situation is looking for a unit with a reputation for having low latency.

In my experience, Elgato has the best products to go with. They are a little more pricey than other competitors, but they're worth it for future-proofing. Their software support is excellent as well.