Here’s a review of the MakeMHz HDMI mod for the original Xbox. This mod taps the digital audio and video signals before they’re ever send to analog, making it a true digital-to-digital HDMI solution
MakeMHz Xbox HDMI: https://makemhz.com/collections/xbox/products/xboxhdmi
OpenXenium ModChip: https://makemhz.com/products/openxenium
The review also goes over alternatives to an internal mod, demonstrates how dual-output would work with external adapters and shows how it looks with the mCable!
Xbox Resolution Compatibility List: https://en.everybodywiki.com/List_of_Xbox_games_with_alternate_display_modes
HDMI Splitter: https://amzn.to/3i0UlWF
HDMI Splitter with audio extractor: https://amzn.to/2ROpWQt
HDMI to Component Converter: https://amzn.to/3iRyOAU
Quality Component Cables: https://amzn.to/3iRKsvq
Chimeric Systems HDMI Adapter: https://www.chimericsystems.com/product/hdmi-video-adapter/
Xbox2Wii Adapter: https://classicgamestore.ch/xbox2wii-component-adapter?sPartner=RetroRGB
Xbox2Wii Pro: https://classicgamestore.ch/xbox2wii-component-adapter?sPartner=RetroRGB
High Quality Wii Component Cables: https://amzn.to/3dAzuIG
Also, Modern Vintage Gamer did an excellent review of it as well (below), so please check that out if you’d like another perspective!