I have a pair of Bose QC35's, and they work fine on my iPhone/iPad and on Windows, but when I connect them to Ubuntu, the bluetooth connection works, but whenever I play some audio, a lot of garbled hissing noise is made. I have set them up again and again using the default connection interface, and with blueman. I am using Ubuntu Gnome if that is important. Any help would be appreciated, thanks.
In the sound settings, use
High Fidelity Playback (A2DP Sink) mode for the headphones. The hissing will stop.
One caveat is that the headphone's microphone won't work in this mode. This might be an issue with the headphones themselves. I experience the same issue with android when I get a call (android uses A2DP by default and switches to HSP when you get a call).