On the ESP32-S3 ADC2 is shared with Wifi, but I don't think that's the case for ADC1. I made headway by throwing away all their boilerplate code and setting up the raw peripheral registers myself. I actually prefer it that way without all the abstraction underneath. Was getting nice results at 80kHz sample rate.

Would love to turn it into a write-up as I'm not sure anyone has done this before with that chip (at least I couldn't find any sample code around). It's actually all in MicroPython at the moment to boot... but wouldn't be hard to convert to C (and might even clean things up due to the more natural fit of that language working with bitfields). What I'd really like is to make it into a DMA-based ADC module for MicroPython but I'm not familiar enough with compiling that platform from scratch, particularly on Windows.