Pairing Bose QC 35 over Bluetooth on Fedora

I have these headphones as well, along with a handy laptop running Fedora 24. After chatting with one of the Bluez developers on IRC, I have things working. Below is what I've found. (Note that I know very little about Bluetooth so I may be using incorrect terminology for some of this.)

The headphones support (or at least say they support) bluetooth LE but don't support LE for pairing. Bluez does not yet support this and has no way to set the supported BT mode except statically in the configuration file. You can use the headphones over regular bluetooth just fine, though. This happens to be the reason Bluez 4 works; it doesn't really support LE.

So, create /etc/bluetooth/main.conf. Fedora 24 doesn't come with this file so either fetch a copy from Upstream, find the line containing

#ControllerMode = dual

and change it to:

ControllerMode = bredr

or create a new file containing just:

[General]
ControllerMode = bredr

Then restart bluetooth and pair. (I did this manually via bluetoothctl, but just using the bluetooth manager should work.)

Now, this got things working for me, though if you don't force pulseaudio to use the A2DP-Sink protocol, the headphones will announce that you have an incoming call for some reason. However, my mouse requires Bluetooth LE, so I went in and removed the ControllerMode line. And... the headphones still work, as well as the mouse. I guess that once they are paired everything is OK.

I read up on your specific headphones, and they use Near Field Communication (NFC) to facilitate pairing, and this was mentioned as specifically added in Bluez 5.3, although, it mentioned on at least one blog "NFC comes built in to the new keyboard, but unfortunately Gnu/Linux doesn’t support NFC well yet. Although NFC support is built in to the Linux Kernel, neither Gnome nor KDE have any support for it, and the number of NFC enabled apps in my Fedora 20 repository is princely zero. NFC won’t help me out pairing my device, so we need to do it the old fashioned way instead..." So then, that puts us back to your approach.

However, Bluez 5.3 did not have support for pairing with devices (such as Bose your headphones) that use a PIN code for pairing.
There is a bug report from the previous verions, on another distribution. So although this is not specifically reported on Fedora, the official Bluez site does not specifically mention a fix, at least from what I can see.

So this feature is not supported; and at least for now that is the answer.

As well, as you suspected, there could be other issues, like needing a specific proprietary drvier, unless you have already ruled that out (i.e. by testing the headphones class-compliant on OSX or Windows or whatever they support). I really highly suspect that is the case, or it gives you or another something to springboard off of.