physically, i wired the MQ2 as such:
MQ2===================NodeMCU.
A0-------------------------------------A0
D0-------------------------------------not used
GND-----------------------------------GND
VCC------------------------------------5V
on the ESPHome config, i have it as such:
currently it is sitting by my window. i dont have any of these fumes to test it out atm: i-butane, propane, methane ,alcohol, Hydrogen, smoke. i will try to get some isopropyl alcohol by tomorrow.