Comment by simlevesque

The first american GameCube (DOL-001) has a port that can be used to output in 720i. With that port you can use a device like the popular Carby or any device that uses the GCVideo software. You could make your own.

For upscaling there's Prism HD, a more expensive device

https://insurrectionindustries.com/product/carby-v2/ https://github.com/ikorb/gcvideo https://retro-bit.com/prism-hd/