List of materials:
- 4 digits 7 segment with 2 x TM74HC595 shift registers. (schematic)
- HC-SR04 Ultrasonic Ranging Module (datasheet)
You can buy a Segger JTAG J-Link clone for few USD on ebay, aliexpress, dx, ...
If you try to update its firmware with the official Segger tool, you'll brick the probe.
Don't worry, smart people have already put a checklist to restore a working firmware and even update it to the latest official version. I just put all the needed info into one single page.