MMI Supplementary Service codes not working: SUPS Failure
a standard gsm code like *#21#
(check state of diverted calls) should work but I always get:
sudo mmcli -m any --3gpp-ussd-initiate="*#21#"
error: couldn't initiate USSD session: 'GDBus.Error:org.freedesktop.libqmi.Error.Protocol.SupsFailureCase: Couldn't originate USSD operation: QMI protocol error (92): 'SupsFailureCase''
see https://en.wikipedia.org/wiki/Unstructured_Supplementary_Service_Data#Code_table
I use HoT (Austria) but Angus reproduced the same thing in Canada.
Does anyone know why that is? Do we know what our modem implements?