Bluetooth speaker volume buttons have no effect on speaker volume

I just bought a Bose Soundlink Flex portable bluetooth speaker. I am using Ubuntu 22.04 with unmodified bluetooth configuration. It plays well and I can control the volume using the usual Linux controls like volume control in the top bar and pavucontrol and Firefox volume control when playing video. But when I try to change the volume by using the volume buttons on the speaker, there is no reaction. Volume stays unchanged. When the speaker is connected to my Samsung Galaxy A22 5G phone I can use the speaker buttons as expected. When I connect from Linux, I can see two devices MyBose and LE-MyBose, but I can only connect to MyBose. Using Bluetooth Manager applet Info option I see the following:

C8:7B:23:8D:EE:36
public
MyBose
MyBose
0x240414
0x0000
audio-card
yes
yes
no
no
yes
00001101-0000-1000-8000-00805f9b34fb Serial Port
0000110b-0000-1000-8000-00805f9b34fb Audio Sink
0000110c-0000-1000-8000-00805f9b34fb Remote Control Target
0000110d-0000-1000-8000-00805f9b34fb Advanced Audio
0000110e-0000-1000-8000-00805f9b34fb Remote Control
0000111e-0000-1000-8000-00805f9b34fb Handsfree
0000112f-0000-1000-8000-00805f9b34fb Phonebook Access (PBAP) - PSE
00001200-0000-1000-8000-00805f9b34fb PnP Information
bluetooth:v009EpBC60d0301
/org/bluez/hci0

sudo bluetoothctl show

Controller 70:66:55:C9:5D:C8 (public)
    Name: argon
    Alias: argon
    Class: 0x007c010c
    Powered: yes
    Discoverable: no
    DiscoverableTimeout: 0x000000b4
    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                   (00001108-0000-1000-8000-00805f9b34fb)
    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: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
    UUID: Device Information        (0000180a-0000-1000-8000-00805f9b34fb)
    UUID: Generic Access Profile    (00001800-0000-1000-8000-00805f9b34fb)
    UUID: Handsfree Audio Gateway   (0000111f-0000-1000-8000-00805f9b34fb)
    UUID: Audio Source              (0000110a-0000-1000-8000-00805f9b34fb)
    UUID: OBEX File Transfer        (00001106-0000-1000-8000-00805f9b34fb)
    Modalias: usb:v1D6Bp0246d0540
    Discovering: no
    Roles: central
    Roles: peripheral
Advertising Features:
    ActiveInstances: 0x00 (0)
    SupportedInstances: 0x05 (5)
    SupportedIncludes: tx-power
    SupportedIncludes: appearance
    SupportedIncludes: local-name

Any ideas to solve this ?