I would not be surprised if they do trade with cryptocurrency considering that cryptocurrencies are really hard to trace compared to the conventional means of trading such as cash or valuable resources. Unless their funders don’t really accept cryptocurrency and they stick with the older methods of payment.
By the way, just to make it clear. I am not in any way planning to make a terrorist group or insurgency, I am just asking out of curiosity as I can see that those terrorist groups or insurgencies in the news must get their funding from somewhere and I was wondering what means do they use to trade for their equipment.