You will be able to find the Red Mile race on Porrima III, in the Porrima system.
Head to Porrina, then Porrina 3 (the third planet from the sun). But even if you’re eavesdropping conversations in New Atlantis, you will get the prompt to visit here right away – though I would advise getting some levels under your belt first.
No matter what quest you’re following, there’s a chance you’ll end up here anyway: I was taken here as part of the Ranger questline (a few main missions into the overall line operating out of Akali city). Protected by a private merc group, and home to a casino and bar that puts me in mind of ‘Canary Wharf on a deserted planet’, the Red Mile is not a locale for the faint of hearts. What’s the point of existing in the government-free frontiers of the galaxy if you can’t host glamorous, immoral gauntlets of death for feckless space iditos that want to make a quick buck? That’s the question Bethesda dares to ask with the Starfield Red Mile – a small casino-like outpost in the Porrima system that is an exclusive members-only affair.