#turn bluetooth on:
sudo /etc/init.d/bluetooth restart
# make it automatic on boot
sudo systemctl enable bluetooth
# reinstall bluetooth
sudo apt --purge --reinstall install bluetooth bluez blueman pulseaudio pulseaudio-module-bluetooth
# at
sudo nano /etc/pulse/default.pa
# add load-module module-bluez5-discover
# then
sudo killall pulseaudio
pulseaudio --start
sudo systemctl restart bluetooth.service
rm -rf ~/.config/pulse/
# Log out
# Log back in
# go to desktop settings/'sound'
# insert headphones
# Go to 'input' section
# Do microphone audio test on each available device
# Follow this link
https://kumarvinay.com/how-to-enable-bluetooth-headset-microphone-support-in-ubuntu-20-04/