That info can be found with hciconfig -a

hci0:   Type: BR/EDR  Bus: USB
    BD Address: 5C:93:A2:A3:59:56  ACL MTU: 1022:8  SCO MTU: 183:5
    UP RUNNING PSCAN ISCAN 
    RX bytes:1146297 acl:195 sco:10904 events:84051 errors:0
    TX bytes:72067880 acl:83905 sco:10762 commands:83 errors:0
    Features: 0xff 0xfe 0x0d 0xfe 0xd8 0x7f 0x7b 0x8f
    Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
    Link policy: RSWITCH HOLD SNIFF 
    Link mode: SLAVE ACCEPT 
    Name: 'ubuntu-0'
    Class: 0x6c0100
    Service Classes: Rendering, Capturing, Audio, Telephony
    Device Class: Computer, Uncategorized
    HCI Version:  (0x7)  Revision: 0x3101
    LMP Version:  (0x7)  Subversion: 0x1
    Manufacturer: Atheros Communications, Inc. (69)

The HCI Version (0x7) indicates version 4.1

The mapping of HCI version to the bluetooth specification versions are:

| HCI version | Bluetooth version |
|-------------|-------------------|
| 0 (0x0)     | 1.0b              |
| 1 (0x1)     | 1.1               |
| 2 (0x2)     | 1.2               |
| 3 (0x3)     | 2.0               |
| 4 (0x4)     | 2.1               |
| 5 (0x5)     | 3.0               |
| 6 (0x6)     | 4.0               |
| 7 (0x7)     | 4.1               |
| 8 (0x8)     | 4.2               |
| 9 (0x9)     | 5.0               |
| 10 (0xa)    | 5.1               |

Also see How to check Bluetooth Adapter version in Windows 10