In my experience, the ESP32's ADC isn't noisy so much as buggy. When using the most straight forward mode of operation, software triggering, the ADC frequently

In my experience, the ESP32's ADC isn't noisy so much as buggy. When using the most straight forward mode of operation, software triggering, the ADC frequently spits out garbage. It's almost as if it's an internal pin mux problem. The ADC can instead be clocked by the I2S peripheral, and when doing so it seems to bypass that particular bug. I did that for a hobby project. I was trying to detect 500uS wide pulses, and I went from regularly missing them to getting every single one. I suspect that the software trigger mode goes through an intermediate MCU in the guts of the ESP32, and there's some race conditions in it's firmware.