Sweet! FYI for the others:
"/home/bernhard/.platformio/penv/bin/python" "/home/bernhard/.platformio/packages/tool-esptoolpy/esptool.py" --chip esp32 --port "/dev/ttyUSB0" --baud 460800 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 40m --flash_size 4MB 0x1000 /home/bernhard/.platformio/packages/framework-arduinoespressif32/tools/sdk/esp32/bin/bootloader_dio_40m.bin 0x8000 /home/bernhard/Desktop/wd/BierBot-Brick-ESP32/.pio/build/az-delivery-devkit-v4/partitions.bin 0xe000 /home/bernhard/.platformio/packages/framework-arduinoespressif32/tools/partitions/boot_app0.bin 0x10000 .pio/build/az-delivery-devkit-v4/firmware.bin
So there is a bootloader being flashed! 
Is there a way to package all of that into a single binary that I can give to others? Pragmatic way would be to download it from the ESP32…
Edit: Actually, that’s suggested here: ESP32: How to create one, solid firmware package that will include bootloader, etc. in a single file?