After finding a related bug report [1] (reported against bluez) I tried to connect the speakers after boot several times (around 20 attempts with two different notebooks). Before that I didn't realize that I _always_ have to restart bluetoothd (or deactivate and reactivate the bluetooth adapter) so that the speakers are added as output device when I connect them… So now I can confirm that.
This report is probably a duplicate of #772717. [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=772717 -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org