Having had many contacts with turd world countries where conventional banking has collapsed, I can guarantee that tether is becoming an on-ramp-off-ramp to transport money in and out of said countries.

I think swift, visa/mc/amex/discover and then Bitcoin. And it will be impossible to really know because Bitcoin lightning is surveillance resistant by design. Best they can do is ask custodial wallets for their volumes. Noderunners are close enough to anonymous except their IP addresses, and the general rule is they don't keep records or archive the tx logs. Even if they did, AMP complicates it even more and no other clearinghouse can do this - route payments across multiple paths, that nobody in there knows more than amounts and directions. Both halves of the route are private to each end...