On version 3.105 everything worked fine.
After updating to version 3.215, the device does not see the built-in EC20 modem and says “No Modem device found. Plug in your USB modem to start”
After restoring to 3.105 again everything is ok.
Due to the outdated base system OpenWRT 19.07 I changed the system to clean OpenWRT 22.03
Are you going to update your system to version 22.03 for this device?