I often find the "legal standing" argument to be fundamentally misapplied. In this case for example, any US citizen should be deemed as having legal standing for the simple reason that a rigged district anywhere impacts all US citizens in very direct ways.
Who gets to vote in the US legislature is a matter of Constitutional concern and protection for every citizen.
Of course, most supposed Constitutional legal so-called experts would disagree, but that's because most of them are out to protect the plutocracy from the citizenry. Most such Constitutional legal-experts refuse to follow logical legal arguments. They don't seek to overturn things that are earthshakingly important.