Interesting post.
My recently purchased low mileage 2023 5.7 Liter Dodge Challenger's coolant had what is described in this post "filthy dirty looking" anti freeze in the radiator coolant over flow/recovery tank(the Challenger/Charger/Chrysler 300 cars do not have an radiator set up like the RAM trucks that have a traditional radiator with the cap and a recovery tank) ... my suspicion is exactly what is described in this post.
I took my car back to the dealer and they(service writers/mechanics)didn't have a clue what it could be, nevertheless, I had them flush out everything(three hours wait, lol) and refill with clean coolant ... no good.
I ended up buying four gallons of MOPAR OAT coolant and performed my own flush to remove what is probably casting sand that wasn't cleaned out from the factory ... sad ... again, the car(s)set up is different that the RAM truck and is a little bit more involved.
It's also sad that my local CRJD couldn't resolve my issue, let alone know what it could possibly be ...
my apologies, no pics taken ... I was more concerned just getting that crap out. It's a crying shame that the money these "Stellantis" vehicles, cost the company can't or doesn't have good quality control ... again, that's sad.