Having an idea of what sort of budget you are considering would be useful. If you are coming from a sub-$200 RX570 though, then I imagine you might not be looking at $500+ cards.
Due to a shortage, graphics cards in general are priced quite poorly at the moment though, at least at US online stores, where anything you can find in stock is typically at around double the suggested price. So it's probably a really bad time to be buying a graphics card right now, and that will likely continue for a number of months to come. It might be worth just sticking with your existing card for the time being, unless the pricing and availability situation is significantly better where you are.
As for what is the "best GPU for an i5-10400F", that...