Udev service for temporary solve bug 92102 https://bugs.freedesktop.org/show_bug.cgi?id=92102

20-bt-auto-enable-a2dp.rules

# /etc/udev/rules.d/20-bt-auto-enable-a2dp.rules
# hxss
SUBSYSTEM=="bluetooth", ACTION=="add", RUN+="/home/hxss/.config/scripts/xorg/bt-auto-enable-a2dp.sh"

bt-auto-enable-a2dp.sh

#!/bin/sh

# Dependencies:
# * bluez-tools
# * expect
# * perl

function enable_a2dp() {
	# run connect command in bluetoothctl and wait for resolve of services
	expect <<< "
		spawn bluetoothctl
		send \"connect $mac\r\"
		log_user 0
		expect -re \".*Device $mac ServicesResolved: yes\"
	"
	# enable card in pulseaudio
	pactl set-card-profile $pulsecard a2dp_sink
	logger -p info "mac $mac enabled"

	headsetname=`bt-device -l | perl -ne '/(.*) \('$mac'\)/ and print "$1\n"'`
	notify-send 'Headset connected' "$headsetname" --icon=blueman-headset
}

function search_headsets() {
	sleep 1
	# in all added devices
	for mac in `bt-device -l | perl -ne '/.*\((.*)\)/ and print "$1\n"'`
	do
		# search for connected device with AudioSink service
		if [[ `bt-device -i $mac | perl -00 -ne '/.*Trusted: 1.*\n\s*Blocked: 0.*\n\s*Connected: 1\n\s*UUIDs: .*AudioSink.*/ and print "1\n"'` ]]; then
			logger -p info "found mac: $mac"
			# convert mac to pulse card name
			pulsecard=`perl -pe 's/:/_/g' <<< "bluez_card.$mac"`
			enable_a2dp
		fi
	done
	echo "search done"
}

logger -p info "${BASH_SOURCE[0]}"

# get script owner name
user=`stat -c %U $0`

if [ "$user" == `whoami` ]; then
	# if script runned by owner - start main function
	search_headsets
elif [ "`w -hs $user`" ]; then
	# else if user session exist(to prevent running on system startup) - run script from user
	machinectl shell --uid=$user .host ${BASH_SOURCE[0]}
fi

Works great in Manjaro linux. Thanks for that script!

Side note: For me (Manjaro) it wasn't the package bluez-tools. I needed bluez-utils.
Also thank you very much for that script <3

Nice, I should try this. Would you mind adding a license to your gist, if it work well (and your license allows), I might package it for nixos. Here's an example of what people seem to do to license their gist:

https://gist.github.com/martinbuberl/c0de29e623a1e34d1cda7e817d18bafe

I don't know what I am missing but I can get this to work on Manjaro. My headphones always default to SBC even if I have needed ldac modules etc installed.

Great workaround! For my case (using Linux Mint 19.1, based on Ubuntu), I had to add some extra steps:
a. changing line 1 of the script #!/bin/sh to #!/bin/bash (as sh in Mint/Ubuntu is a very basic shell interpreter, unable to follow your script)
b. creating a systemd service pointing to your script named "auto-enable-a2dp.service" (see: https://www.pcsuggest.com/run-shell-scripts-from-udev-rules/)
c. changing line 3 of the rule, replacing RUN with TAG+="systemd", ENV{SYSTEMD_WANTS}="auto-enable-a2dp.service"
d. installing a last dependency 'sudo apt install systemd-container'

It is still possible to debug the service by tapping 'systemctl status auto-enable-a2dp.service'

Worked for me. Thanks :)

peacecop@peacecop-HP-ProBook-4520s:~$ ./bt-auto-enable-a2dp.sh
./bt-auto-enable-a2dp.sh: 8: Syntax error: "(" unexpected

It Works well on Manjaro KDE.