nostr:npub1rvwnhzkvllph6ulm93fg9wvs4agaqwgagpkyl27q6m5wlp6g9gqqvcxgew depends how retro you mean.
I got this Kaico cable which converts an original Xbox to HDMI - https://shkspr.mobi/blog/2022/07/review-kaico-xbox-hmdi-cable-optical/
They also do specific converters for DreamCast and other consoles. Or an OSSC which should handle most things.