Hi, welcome to JustAnswer!. This is Ed.
Suggestions? Certainly so!
A "CHECK ENGINE-GAS CAP" combo comes up because the original infraction coincides with a fuel fill increase... and then the evaporative system leak failure occurs. It's a rationality-based code, one that suggests that since you had the problem after filling the tank that the gas cap might be loose. This code (a P0457) gives the customer a chance to check cap tightness before a real ("hard") code of P0456 or greater is set. Any sort of evap system failure can set the P0457 code if it happens close enough to a fuel fill event, but it doesn't necessarily mean that the problem is in the cap area. Sometimes it is...sometimes not.
By now, we can rule out the gas cap. You may have an actual evaporative system leak, but chances are better (playing probability here) that the detection system is at fault.
You've got a new ESIM, which is a major contributor to these sort of problems. You might have a broken wire to the ESIM, which is pretty exposed on the underside of the vehicle and any sort of break will simulate an actual leak-type event.
Another possibility is more likely if your Pacifica is driven on dusty roads, which can pack up the evaporative system filter, located just past the ESIM. If the filter becomes restricted, there may be no pressure difference between sides of the ESIM, meaning it can't detect vacuum. If that happens, the ESIM is just along for the ride and will never send an electrical state change signal... once again, the same thing as an actual system leak. I wouldn't expect this to be a realistic issue on paved road travel or if the vehicle has never been immersed or packed with mud from below, besides the dusty road thing.
I don't know what your capacity for crawling around under the car with a voltmeter is, so I'll wait for your reply. I can go into much greater detail for electrical testing, but it will all be far inferior to what the dealer should be able to do with their (our) scan tool and leak detection machine. It's going to be hard work and might not prove conclusive, but if you want to give it a go, I'll do what I can.
So, the short answer would be to look for broken wiring to the ESIM (only two wires used) or for a packed evap system filter.