Hi Sebastian,
The libraries you used need an update: (I changed the platformio.ini file accordingly):
lib_deps =
alanswx/ESPAsyncWiFiManager@^0.31
ayushsharma82/AsyncElegantOTA@^2.2.7
marvinroger/AsyncMqttClient@^0.9.0
me-no-dev/ESP Async WebServer@^1.2.3
bblanchon/ArduinoJson@^6.21.3
But I am getting an error regarding get and setHostname…?
Do you have any udated version or a working binary for ESP8266?