Hello. I bought RB5009, updated to the latest version 7.9.1. I connected a GSM modem to the USB port: miniPCI-e SIMCOM SIM7600E-H modem + USB dongle. The modem sees the router, defined normally - but you can not change anything in the settings, you can not disable the interface. At any action the following error appears: Couldn't change Interface <lte1> - IPv6 not supported for this device (6). If you try to make settings through the terminal, you get the error: failure: IPv6 not supported for this device. Earlier this modem was connected and worked with hAP AC^2 with 6.49.6 firmware. I tried to enable / disable IPv6 (disable-ipv6: no \ yes) - did not work.
If you connect another USB modem (like ZTE \Huawei) - everything works without problems.
How can I solve the problem with SIMCOM SIM7600E-H in 5009?

Sorted it out. You can close and delete the topic. The mystery was simple - it was necessary to change the IP Type in APN to IPv4....

Better not delete it. In the future somebody else could be facing the same issue.
https://xkcd.com/979/