Webpage: https://docs.openmqttgateway.com/upload/binaries.html#esp32 Link is currently this: https://github.com/espressif/arduino-esp32/raw/master/tools/sdk/bin/bootloader_dio_80m.bin It should now be this (note "esp32" folder after "sdk"): https://github.com/espressif/arduino-esp32/raw/master/tools/sdk/esp32/bin/bootloader_dio_80m.bin