https://www.macrumors.com/2023/09/28/iphone-15-usb-c-power-banks/
A range of different power banks are affected, and because of the wide number of them on the market, it is impossible to list the models that are non-functional. One version that fails to work is the Anker PowerCore Slim 10K PD, and a customer who contacted Anker was told that the only way to get the power bank to charge the iPhone is to use the USB-A port.
“It seems that due to the iPhone 15 series' reverse charging function, the USB C's port charging of Anker PowerCore Slim 10k PD will be influenced, which does not have a solution currently. The only way to get your iPhone charged is to use the USB A port.
Anker will do more tests on all of our power banks to see whether this is the issue with certain power banks and try to get a solution.”