Sony WF-L900 LinkBuds Bluetooth Earbuds not recognized as audio device

I am trying to connect my Sony WF-L900 LinkBuds to my laptop with Ubuntu as bluetooth headset. The device is found and I can pair without issue, however, it does not appear as audio device to select. This happens with both Ubuntu 21.10 and the current daily build of the upcoming ubuntu 22.04.

The following this I have been checking:

• PulseAudio and all required Bluetooth modules are installed module-bluetooth-discovery
• The device can be paired (via bluetoothctl)

To me it seems like the device does not advertise its audio capabilities through the GATT services listed when connecting:

$ bluetoothctl connect E3:47:4C:CF:CA:23 
Attempting to connect to E3:47:4C:CF:CA:23 
[CHG] Device E3:47:4C:CF:CA:23 Connected: yes
Connection successful
$ bluetoothctl info E3:47:4C:CF:CA:23 
Device E3:47:4C:CF:CA:23 (random)
    Name: LE_LinkBuds
    Alias: LE_LinkBuds
    Paired: yes
    Trusted: yes
    Blocked: no
    Connected: yes
    LegacyPairing: no
    UUID: Generic Access Profile    (00001800-0000-1000-8000-00805f9b34fb)
    UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
    UUID: Amazon.com Services, Inc. (0000fe03-0000-1000-8000-00805f9b34fb)
    UUID: Google                    (0000fe2c-0000-1000-8000-00805f9b34fb)
    UUID: Vendor specific           (45c93e07-d90d-4b93-a9db-91e5dd734e35)
    UUID: Vendor specific           (55f80aef-d89f-41a4-9e36-0ffc88dc81ce)
    UUID: Vendor specific           (5b833e05-6bc7-4802-8e9a-723ceca4bd8f)
    UUID: Vendor specific           (5b833e06-6bc7-4802-8e9a-723ceca4bd8f)
    UUID: Vendor specific           (5b833e0a-6bc7-4802-8e9a-723ceca4bd8f)
    UUID: Vendor specific           (67a846ad-de3e-451b-a6d8-7b2899ca2370)
    UUID: Vendor specific           (91c10d9c-aaef-42bd-b6d6-8a648c19213d)
    UUID: Vendor specific           (dc405470-a351-4a59-97d8-2e2e3b207fbb)
    UUID: Vendor specific           (fe59bfa8-7fe3-4a05-9d94-99fadc69faff)

My bluetooth controller looks like this:

$ bluetoothctl show
Controller E4:A7:A0:C6:B3:52 (public)
    Name: sosa5001-laptop
    Alias: sosa5001-laptop
    Class: 0x003c010c
    Powered: yes
    Discoverable: yes
    DiscoverableTimeout: 0x00000000
    Pairable: yes
    UUID: Message Notification Se.. (00001133-0000-1000-8000-00805f9b34fb)
    UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f9b34fb)
    UUID: OBEX Object Push          (00001105-0000-1000-8000-00805f9b34fb)
    UUID: Message Access Server     (00001132-0000-1000-8000-00805f9b34fb)
    UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
    UUID: IrMC Sync                 (00001104-0000-1000-8000-00805f9b34fb)
    UUID: Vendor specific           (00005005-0000-1000-8000-0002ee000001)
    UUID: Headset AG                (00001112-0000-1000-8000-00805f9b34fb)
    UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
    UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
    UUID: Phonebook Access Server   (0000112f-0000-1000-8000-00805f9b34fb)
    UUID: Device Information        (0000180a-0000-1000-8000-00805f9b34fb)
    UUID: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
    UUID: Generic Access Profile    (00001800-0000-1000-8000-00805f9b34fb)
    UUID: Headset                   (00001108-0000-1000-8000-00805f9b34fb)
    UUID: Audio Source              (0000110a-0000-1000-8000-00805f9b34fb)
    UUID: OBEX File Transfer        (00001106-0000-1000-8000-00805f9b34fb)
    Modalias: usb:v1D6Bp0246d053C
    Discovering: no
    Roles: central
    Roles: peripheral
Advertising Features:
    ActiveInstances: 0x00 (0)
    SupportedInstances: 0x05 (5)
    SupportedIncludes: tx-power
    SupportedIncludes: appearance
    SupportedIncludes: local-name

This is with Bluez 5.60:

$ bluetoothctl version
Version 5.60

What am I missing in order to be able to use my Sony WF-L900 LinkBuds as headset with Ubuntu 21.10 or later?

I checked on Sony's setup steps for windows/mac, and it mentions using the case for pairing (see source link). I did this on Linux Mint and it worked, it paired (device shows as LinkBuds, do not connect to LE_LinkBuds) and it works now as audio input (mic) and output (system sound). I don't see why it shouldn't work on Ubuntu as well. Hope this is helpful as I had issues with it as well and didn't understand why I was having the same as you.

(source: https://helpguide.sony.net/mdr/linkbuds/v1/en/contents/TP1000448418.html)