I live in the US and that general style of gas meter (diaphragm) is the norm. None of the easy options worked for me but I stumbled across folks using magnetometers to sense the movement of the diaphragm and went that route. Had it up for a couple months and it’s been working flawlessly. The beauty is I feel like it’s even more resilient than other options, as what it’s sensing is so large, as long as the sensor doesn’t just completely fall off the side of the meter you’re unlikely to find it has stopped working as intended.
Here’s a post I made in another thread with the info on my setup.
Hopefully it’s helpful for someone else, as I was just about to give up on capturing my nature gas consumption before I stumbled on this method.