Sorry for the noise. The board came with a inverted/mirrored pinout diagram! I've already alert the store. Everything is working now and there is no difference in the RTM initialization.

Thank you @WiFive. I've check both logs (for the Allnet-IOT-OLED and the standard ESP32-WROOM-32) and both seem to use the same 80 MHz clock source for the RMT initialization.

ESP32-WROOM-32 log (working):

I (0) cpu_start: Starting scheduler on APP CPU.
D (297) heap_init: New heap initialised at ...

I'm able to read DS18B20 sensors using the example code provided in this repository https://github.com/DavidAntliff/esp32-ds18b20-example .

It works well using a standard Espressif ESP32-WROOM-32 (aka ESP32-DevKitC), which uses a 40 MHz XTAL.

I'm not able to run the same example using an Allnet ...

I had the same problem with an ESP32+OLED https://www.allnet.de/lp/iot-wlan-display/

I've set the Main XTAL frequency to Autodetect and it works.