And indeed it's also useful to open up the app and check well known chargers. I was used to having a pretty good deal on Engie chargers during my trips to France last year and on the last holiday. But during my last trip, the price per kWh on Electroverse had tripled, making it more expensive than using a debit card.
And now it's slightly lower again...
I have probably a half dozen cards in the armrest for the various providers, Shell, Electroverse, Chargepoint, Plugsurfing, etc... The only way to be sure to get the best deal is opening every app at a charging station and check who the cheapest is...