Compile and install BlueZ on Ubuntu 21.10

Install essential packages

sudo apt install build-essential libglib2.0-dev libdbus-1-dev libudev-dev libical-dev libreadline-dev python3-docutils

Download, compile and install latest BlueZ

BlueZ » Download
tar xvf bluez-5.63.tar.xz
cd bluez-5.63
sudo make install

Enable BlueZ experimental

sudo nano /lib/systemd/system/bluetooth.service
ExecStart=/usr/local/libexec/bluetooth/bluetoothd --experimental
sudo systemctl daemon-reload
sudo systemctl restart bluetooth
sudo systemctl status bluetooth
● bluetooth.service - Bluetooth service
     Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)
     Active: active (running) since Sat 2022-03-05 11:07:12 HKT; 10s ago
       Docs: man:bluetoothd(8)
   Main PID: 39772 (bluetoothd)
     Status: "Running"
      Tasks: 1 (limit: 9263)
     Memory: 476.0K
     CGroup: /system.slice/bluetooth.service
             └─39772 /usr/local/libexec/bluetooth/bluetoothd --experimental


sudo bluetoothctl
[bluetooth]# list

hcitool is deprecated. Please use bluetoothctl.

In case of bluetooth interface problem

Check if rfkill blocking the bluetooth device

sudo rfkill list
0: phy0: Wireless LAN
        Soft blocked: yes
        Hard blocked: no
1: hci0: Bluetooth
        Soft blocked: yes
        Hard blocked: no

If so

sudo rfkill unblock bluetooth

If the problem still exists, make sure no service uses Bluetooth. Reboot.