It seems that my phone somehow can get APN settings automatically, after inserting my old SIM card to the new phone
m.tinkoff in iOS Mobile Data Network menu appeared automatically, and this correct one for my mobile operator. However, when I’m trying to config some LTE modem to connect to the Internet, I have to config APN settings manually.
How did my phone get correct settings? Is it some database with settings for all mobile operators all over the world supported by Apple, or there is some standard protocol to fetch default after registration in operator network?