I like the project a bit. However, flare gas usage for mining is only "beneficial" for the environment if there is not really another way to use the energy, because the extraction sites are far away from infrastructure to transport the gas to other places.

There is an alternative that is also being explored: on-site LNG production (liquefaction). However, as this is a more complex and expensive operation, it is suited more for relatively big extraction sites. So currently on very small extraction sites, mining is indeed the best solution probably together with some types of scientific computing. (No, AI is probably not, because AI needs big data centers with lots of connected GPUs). But in the future if LNG production equipment becomes smaller and then Bitcoin mining could lose its "edge" here.

Most environmentally friendly mining technique would be "peak-scalping" of PV (at the hours around midday) and wind energy (during windy days), although this is of course not very profitable due to the low mining time (ASICs sit idle during most of the day). With some battery power however it is possible that this is already profitable on good sites (e.g. sunny highland climates).