Detect if (LTE-)Fallback is active
I would like to get a notification or start an automation if my internet connection switches from DSL to the fallback connection (USB-connected 4G-Stick).
Maybe a contact sensor that's opening if the dsl-sync is missing and mobile data is used.

For example: When mobile data is used I could shutdown some devices from an automation and reduce the mobile data usage.

https://service.avm.de/help/en/FRITZ-Box-7590/019/hilfe_mobilfunk_usb_modem