My SIP provider, CallCentric. has a web page for configuring various ATA boxes and softphones, including Grandstream, but of course not for Gnome dialer. That got me up and running with the Grandstream very quickly, but the Grandstream device configuration web form had drifted a bit from the CallCentric instruction page, so there was some uncertainty and anxiety. The various softphone apps had drifted much more.
My L5 will register over wifi, but not (AweSIM) mobile data.