iodéOS 7.5 – VoLTE broken with Sunrise network (Switzerland) – proven carrier-specific, not device-specific

Thanks for this writeup. Since we are discussing the issue in this thread: Calls not working on FP4 patch 7.5 - #9 by rik lets stay over there with the discussion but post the results back here (as it is more broadly about Sunrise it seems rather than device specific with FP) as a reference as well.