OK. I managed to make it work with fresh firmware version 21.300.05.00.00 on E3372s-153 (AT^SETPORT=“FF;12,16”) and following minimal config:
config interface 'wwan'
option proto 'ncm'
option apn 'MY_APN'
option peerdns '0'
option dns '208.67.222.222 208.67.220.220'
option device '/dev/ttyUSB0'
then uci commit network && reboot. And after reboot I can see wwan0 interface and internet connection is working. It doesn’t show my IPv4 on the interfaces page in LUCI.
It does not use specified DNS servers tho. I think it might be my ISP limitation.
Setting more options, ex. to force lte or persistent connection breaks config and wwan0 is not showing up.