@Stone2019, every BeagleBone Black has a 20 pin CTI header on the back you can use, from the manual:
5.12 CTI JTAG Header
A place for an optional 20 pin CTI JTAG header is provided on the board to facilitate the SW development and debugging of the board by using various JTAG emulators. This header is not supplied standard on the board. To use this, a connector will need to besoldered onto the board.
If you need the JTAG connector you can solder it on yourself. No other components are needed. The connector is made by Samtec and the part number is FTR-110-03-G-D-06.
Regards,