assuming I don't have this quectel module, it seems really strange to me that it only supports ECM mode
Do you have the possibility to check via "picocom" what other features it supports?
can you install "picocom" and check what the outputs of the following AT commands are?
picocom /dev/ttyUSB2
AT
ATI
AT+QCFG=?
also watch:
https://openwrt.org/docs/guide-user/network/wan/wwan/at_commands#picocom
ps: have you tried asking on the forum below what other modes it supports?