Sorry if I break the thread, I'm currently using a broken MUA. Apart from the missing firmware there is also https://bugzilla.kernel.org/show_bug.cgi?id=208965 which seems to be fixed by https://marc.info/?l=linux-bluetooth&m=160378222632366&w=2
So even installing the firmware would not be enough for current Debian unstable. -- Lisandro Damián Nicanor Pérez Meyer http://perezmeyer.com.ar/ http://perezmeyer.blogspot.com/