This page is documenting how user f1ghy added GPIO ports to his H2. He provided the schematics and pictures.

Basic Schematics:

First, pin point the location:

Then solder a small wire on SCL, SDA and 3.3 V pins on the back on the connector P22, and cut it to have 1 cm or 0.5 cm long:

Then place a litle board (pastill PCB (?)) like this. The smalls wires soldered through it. (you may heat the solder with the iron and press the board to prevent the card from moving, and that it is tight on the hackrf card), and solder it:

Now the GPIO connector to have the SCL and SDA to the right pins (only the pins on the PCB side):

Then solder the other wire: 3.3V, VCC, and Ground (GND), and cut off the smalls wires that protrude:

View from the other side:

Then cut your box... so you can close it:

IF you managed to follow that tutorial:

Build your ESP32 companion following the tutorial here: https://github.com/htotoo/ESP32-Portapack/wiki