I made a custom PCB for the heater mode (GitHub - fablab-paderborn/mq7-adapter-board: MQ7 Adapter Board). While that still requires SMD soldering, it is much easier than doing the mode on the existing module. The PCB can be ordered from JLPCB or similar for just a few bucks. You could probably also very easily order a version with all the SMD components already in place from jlpcb for a few more Euros.