I finally gave up and went back to the last working version 1.0.6 for the esp32 board manager in arduino IDE found here: https://dl.espressif.com/dl/package_esp32_index.json
2.0.10 and 2.0.11 can't output open drain pwm from everything I tried.

Your trick did work so far for me too, moving the pinMode call to after the setup allowed for open drain PWM until now. Now some Librairie changed or something else happened but using the same hardware as before and compiled the same firmware as before (with new librairies unfortunately) and nothing...