synced LinkKey but still unknown device.

[tribbloid]

Here is an example output when trying to sync 010203043c41:

registry dump:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\BTHPORT\Parameters\Keys]

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\BTHPORT\Parameters\Keys\64497de78406]
"CentralIRK"=hex:db,c1,6c,53,a3,ba,d3,52,55,47,ac,7b,43,58,5c,05
"010203043c41"=hex:9d,3f,c0,cf,3e,10,72,24,99,35,32,4a,f0,8e,24,85

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\BTHPORT\Parameters\Keys\64497de78406\eb9da4c2bb9d]
"LTK"=hex:6a,fc,74,e4,aa,8b,ef,31,55,3a,bf,4a,f4,15,1e,73
"KeyLength"=dword:00000010
"ERand"=hex(b):2d,9d,21,e8,5e,0e,c7,14
"EDIV"=dword:0000ed35
"IRK"=hex:9b,03,7a,b0,de,82,f4,0d,e8,7b,e9,8f,a9,c6,d5,24
"Address"=hex(b):9d,bb,c2,a4,9d,eb,00,00
"AddressType"=dword:00000001
"CEntralIRKStatus"=dword:00000001
"AuthReq"=dword:0000002d

adapter/device on Linux:

Controller 64:49:7D:E7:84:06 pop-os [default]
Device 01:02:03:04:3C:41 SOUNDPEATS Engine 4

syncing:

Bluetooth Adapter - 64:49:7D:E7:84:06
  CE:NT:RA:LI:RK (# not paired #)

  01:02:03:04:3C:41 (SOUNDPEATS Engine 4 / SOUNDPEATS Engine 4)
    | LinkKey: 9D3FC0CF3E1072249935324AF08E2485 > No change required.
  EB:9D:A4:C2:BB:9D (# not paired #)

error:

blueman-manager 15.47.15 WARNING  ManagerDeviceMenu:141 fail      : fail g-dbus-error-quark: GDBus.Error:org.freedesktop.DBus.Error.Failed: blueman.bluez.errors.DBusFailedError:  br-connection-unknown
 (0)

Looks like there are more authentication in place apart from LinkKey (on Bluetooth 5.3). Is there a way to sniff them out?