Can not connect a bluetooth DAC (FiiO BTR3)

When I try to connect a bluetooth DAC, which is shown as “Paired” and “Trusted”, it first gets connected, then immediately gets disconnected and the bluetooth adapter becomes turned off.

System

OS: Fedora 34 KDE
Kernel: x86_64 Linux 5.12.12-300.fc34.x86_64
Bluez version: 5.59

$ rfkill
ID TYPE      DEVICE      SOFT      HARD
 0 bluetooth hci0   unblocked unblocked
 1 wlan      phy0   unblocked unblocked
$ bluetoothctl show
Controller DC:FB:48:00:3B:3C (public)
        Name: tuxedo
        Alias: tuxedo
        Class: 0x006c010c
        Powered: yes
        Discoverable: yes
        DiscoverableTimeout: 0x00000014
        Pairable: yes
        UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f9b34fb)
        UUID: Handsfree Audio Gateway   (0000111f-0000-1000-8000-00805f9b34fb)
        UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
        UUID: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
        UUID: Headset                   (00001108-0000-1000-8000-00805f9b34fb)
        UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
        UUID: Generic Access Profile    (00001800-0000-1000-8000-00805f9b34fb)
        UUID: Audio Source              (0000110a-0000-1000-8000-00805f9b34fb)
        UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
        UUID: Device Information        (0000180a-0000-1000-8000-00805f9b34fb)
        Modalias: usb:v1D6Bp0246d053B
        Discovering: no
        Roles: central
        Roles: peripheral
Advertising Features:
        ActiveInstances: 0x00 (0)
        SupportedInstances: 0x06 (6)
        SupportedIncludes: tx-power
        SupportedIncludes: appearance
        SupportedIncludes: local-name
        SupportedSecondaryChannels: 1M
        SupportedSecondaryChannels: 2M
        SupportedSecondaryChannels: Coded
$ bluetoothctl devices
Device 40:ED:98:19:8F:18 FiiO BTR3
$ bluetoothctl info 40:ED:98:19:8F:18
Device 40:ED:98:19:8F:18 (public)
        Name: FiiO BTR3
        Alias: FiiO BTR3
        Class: 0x00240418
        Icon: audio-card
        Paired: yes
        Trusted: yes
        Blocked: no
        Connected: no
        LegacyPairing: no
        UUID: Vendor specific           (00000000-deca-fade-deca-deafdecacaff)
        UUID: Serial Port               (00001101-0000-1000-8000-00805f9b34fb)
        UUID: Headset                   (00001108-0000-1000-8000-00805f9b34fb)
        UUID: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
        UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
        UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f9b34fb)
        UUID: Handsfree                 (0000111e-0000-1000-8000-00805f9b34fb)
        UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
        Modalias: bluetooth:v000ApFFFFdFFFF
$ bluetoothctl connect 40:ED:98:19:8F:18
Attempting to connect to 40:ED:98:19:8F:18
[CHG] Controller DC:FB:48:00:3B:3C Discoverable: no
[CHG] Device 40:ED:98:19:8F:18 Connected: yes
No agent is registered
[DEL] Controller DC:FB:48:00:3B:3C tuxedo [default]

What do you see in journalctl --no-hostname -u bluetooth.service? Also, check journalctl --no-hostname -k --grep Bluetooth.

This was a regression in bluez.
With bluez 5.60 works fine.
https://bugzilla.redhat.com/show_bug.cgi?id=1977102