The short answer is to execute the following command:
cp /usr/share/gdm/default.pa ~/.config/pulse/
By googling around a bit I found that
pulseaudio is the audio subsystem in Ubuntu nowadays, and the
pactl command can be used to fiddle with its settings.
This command has quite a few subcommands, the most interesting of which is
pactl list short you can see that there is a module that contains the word
bluez in its name, and it is bluetooth related.
I am using a desktop computer which is not equipped with bluetooth, so there should be no bluetooth-related modules running.
pactl unload-module for each bluetooth-related module did not work, because on reboot the modules were loaded again, and so the error appeared in the log again. One should take hint from the fact that
pactl is billed as a program to "Control a running PulseAudio sound server": it does not actually modify the persisted configuration of the sound server.
By googling around a bit more I found that PulseAudio settings are stored in some
default.pa file, and I found two instances of this file on my system, a fat one under
/etc/pulse/ and a skinny one under
Obviously, the fat one is global PulseAudio settings, and the skinny one is user-specific settings somehow related to the gnome desktop manager.
The contents of the user-specific
default.pa were very interesting, as it contained commands to do precisely what I wanted to do: disable the bluetooth-related modules. It does not disable the
bluez module per se, but by fiddling with
pactl earlier I discovered that disabling the other two bluetooth-related modules has the effect of automagically also disabling the bluez module.
Only problem is, gdm's configuration file is kind of useless to me, because it does not get executed when I log in.
By googling around even a bit more I found that the location for a user-local instance of this settings file is supposed to be
Hence, I reasoned that if I just copied gdm's file to this location on my profile, the problem would be fixed.
And indeed it has.