set bluetooth to disabled by default on debian 10
I'm not sure why Debian developers think it's good to enable bluetooth automatically on boot. I think this is a privacy issue and would prefer bluetooth to be "opt-in". So here's how to make sure bluetooth is turned off by default:
# install tool for disabling bluetooth
# it's a shame debian has no api for this!
sudo apt install rfkill
# setup systemd unit
cat << EOF | sudo bash -c 'cat > /etc/systemd/system/disable-bluetooth-on-startup.service'
[Unit]
Description=Make shure Bluetooth is disabled on system start.
After=bluetooth.service
[Service]
ExecStart=rfkill block bluetooth
[Install]
WantedBy=multi-user.target
EOF
# enable systemd unit
sudo systemctl enable disable-bluetooth-on-startup