Desolder wifi/bluetooth module on a Raspberry Pi 4

I desoldered the wifi chip with hot air gun and Rpi seems to be working just fine. Also disabled wifi and BT in /boot/config.txt (maybe not necessary).

If you want to physically disable Wifi/BT, the easiest way is to disconnect the antenna, or short the antenna output to ground via a 1nF capacitor.

The capacitor is there to avoid having an actual short to ground, which could blow the chip up. 1nF is only 0.06 Ohm at 2.5GHz, so for RF purposes it's as good as a short. A typical antenna impedance is 50 Ohm. Having a 0.06 Ohm path to ground means that only about 0.1% of the transmitter signal will reach the antenna, while 99.9% will be lost. That's about 60 dB attenuation.

Considering the WiFi signal already starts at about -30dBm, attenuation by another 60 will bring the signal down to -90 dBm, which is barely above the thermal noise. This means a few meters away from the device (another -10 dB), you won't be able to receive the signal even theoretically.

Removing the WiFi/BT module is trivial with the right equipment (heat up the board and lift the shield and the IC up with a vacuum pen), but without a schematic I would not give you any guarantees that the rest of the Pi will work once the WiFi chip is gone. And even if the schematic is released, it would be quite a task to analyse it and create a modified device tree for the kernel to correctly understand the new hardware configuration.