@electrik
Hi,
Yes, it's like floating input, but like i said before: on the breadboard its fine, but on the solder one it's floating. And yes, the ground connector are connected to the ESP32 GND pin.
I know that, the MQ2 sensors could require the 24h burning process, but on the breadboard it's fine just after plug-in.
And sure, i could attatch the photo of the connection.