Bluetooth headset does not autoconnect (Ubuntu)

Question

My Bluedio T4 headset does not automatically connect in Ubuntu Linux 20.04 LTS

The device is Trusted and is enabled in PulseAudio /etc/pulse/default.pa. Using Wireshark I can see it's connected shortly to the controler. After a few milliseconds however it sends a Disconnection Request and the device disconnects accordingly.

$ bluetoothctl info 17:07:11:00:00:00
Device 17:07:11:DD:0D:27 (public)
    Name: Bluedio T
    Alias: Bluedio T
    Class: 0x00240404
    Icon: audio-card
    Paired: yes
    Trusted: yes
    Blocked: no
    Connected: no
    LegacyPairing: no
    UUID: Audio Sink                (0000110b-0000-1000-8000-00805f000000)
    UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f000000)
    UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f000000)
    UUID: Handsfree                 (0000111e-0000-1000-8000-00805f000000)

$ cat /etc/pulse/default.pa | grep -B 1 -A 1 module-switch-on-connect
### Use hot-plugged devices like Bluetooth or USB automatically (LP: #1702794)
.ifexists module-switch-on-connect.so
load-module module-switch-on-connect
.endif

No. Time    Source  Destination Protocol    Length  Info
1   0.000000    controller  host    HCI_EVT 13  Rcvd Connect Request
2   0.000030    host    controller  HCI_CMD 11  Sent Accept Connection Request
3   0.001019    controller  host    HCI_EVT 7   Rcvd Command Status (Accept Connection Request)
4   0.175023    controller  host    HCI_EVT 11  Rcvd Role Change
5   0.195976    controller  host    HCI_EVT 14  Rcvd Connect Complete
6   0.196106    host    controller  HCI_CMD 6   Sent Read Remote Supported Features
...
36  0.311036    localhost ()    17:07:11:dd:0d:27 (Bluedio T)   L2CAP   17  Sent Configure Request (DCID: 0x0040)
37  0.317005    controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
38  0.318999    controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
39  0.364021    17:07:11:dd:0d:27 (Bluedio T)   localhost ()    L2CAP   17  Rcvd Configure Request (DCID: 0x0040)
40  0.364073    localhost ()    17:07:11:dd:0d:27 (Bluedio T)   L2CAP   23  Sent Configure Response - Success (SCID: 0x0040)
41  0.366020    17:07:11:dd:0d:27 (Bluedio T)   localhost ()    L2CAP   23  Rcvd Configure Response - Success (SCID: 0x0040)
42  0.369020    controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
43  0.422020    17:07:11:dd:0d:27 (Bluedio T)   localhost ()    SDP 42  Rcvd Service Search Attribute Request : Handsfree Audio Gateway: L2CAP: RFCOMM: [Protocol Descriptor List 0x0004] [Bluetooth Profile Descriptor List 0x0009] [(HFP AG) Network 0x0301] [(HFP AG) Supported Features 0x0311] 
44  0.422245    localhost ()    17:07:11:dd:0d:27 (Bluedio T)   SDP 19  Sent Service Search Attribute Response 
45  0.427979    controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
46  0.479997    17:07:11:dd:0d:27 (Bluedio T)   localhost ()    L2CAP   17  Rcvd Disconnection Request (SCID: 0x0040, DCID: 0x0040, PSM: 0x0001, Service: SDP)
47  0.480021    localhost ()    17:07:11:dd:0d:27 (Bluedio T)   L2CAP   17  Sent Disconnection Response (SCID: 0x0040, DCID: 0x0040, PSM: 0x0001, Service: SDP)
48  0.483982    controller  host    HCI_EVT 8   Rcvd Number of Completed Packets
49  0.687030    controller  host    HCI_EVT 7   Rcvd Disconnect Complete
50  0.748115    host    controller  HCI_CMD 5   Sent Write Scan Enable
51  0.751010    controller  host    HCI_EVT 7   Rcvd Command Complete (Write Scan Enable)

Since this device connects to my Android device without any problems, I have no idea why this is happening.

Answer 1

I have the same problem (but with debian buster and bluedio t6).

I tried changing the option FastConnectable to true in /etc/bluetooth/main.conf, section [General]:

# Permanently enables the Fast Connectable setting for adapters that
# support it. When enabled other devices can connect faster to us,
# however the tradeoff is increased power consumptions. This feature
# will fully work only on kernel version 4.1 and newer. Defaults to
# 'false'.
#FastConnectable = false
FastConnectable = true

Then I restarted bluetoothd, and now the headset connects instantly after turning it on.