Facing problems after upgraded my 4G modem firmware from 9001 to 9011

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I wonder, what currently is the recommended firmware version to have VoLTE calls? Since the one that the uConsole ships with doesn’t seem to work, and the 9011 one seems to have internet issues: Calls use GSM not VoLTE with German carriers - potentially big problem? - #3 by ell1e

It would likely be helpful to users if there was some definite guide on this, perhaps even pinned in the forum and/or added to the Github wiki pages.