How to activate bluetooth device for RTL8723DE?

Support for this bluetooth device had been just added to the 4.17rc kernel.

The code can be easily backported to kernels 4.4 - 4.15. I made a PPA with DKMS packages for bionic and xenial with the updated btrtl module.

It can be installed by

sudo add-apt-repository ppa:hanipouspilot/bluetooth
sudo apt update
sudo apt install btrtl-rtl8723de-dkms

You may also need firmware for this device if it is not there. Look into your /lib/firmware/rtl_bt directory. If there are no rtl8723d_config.bin and rtl8723d_fw.bin files, clone the latest linux-firmware by

git clone git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git

and get the files from there. It is not that hard. Sorry that I forgot to add the firmware to the package.

The DKMS should survive kernel upgrades.

Important!: Ubuntu 18.04 has the 5.3 HWE kernel now. REMOVE this package if you are on 5.3+ kernels. Otherwise BT won't work.