I am using a QMI cellular connection, with OpenWRT 19.07.5. I specify the APN here:
config interface 'wwan' option proto 'qmi' option device '/dev/cdc-wdm0' option apn 'my apn' option modes 'lte'
If I change SIM cards, I must change the APN manually.
I tried out r00ter, and it has a nice method of automatically changing APN when the SIM card is changed. It can be based on a number of parameters including SIM IMSI.
Are there any similar utilities available for OpenWRT?