Thanks! Very interesting. I suspect this has something to do with the network arrangements of simcard-korea. That’s not standard for iphones with ‘normal’ in-country sims. I change my sim every few months and it ‘just works’ without any extra steps.

I think the app is just for you to check your data usage. Things will work without it. Just insert the SIM card and reboot.

The link at the bottom has a profile that sets the APN - it might work without it if you reboot tbh but without being in Korea and having the SIM I can’t verify that. It isn’t the app that he’s talking about.

Didn’t see that. Viewed image on phone and didn’t scroll.

I think it depends on the carrier whether APNs are required. Can be automatically set nowadays with iOS 16 according to https://support.apple.com/en-us/HT201699

I don’t think I’ve _ever_ had to manually set my APN though. I’m now more confused after seeing your link!