That is, in my opinion, impossible to determine. You have no idea which address is a change address, and you have no idea what the objective of a Bitcoin transaction is. Furthermore, no one can count the volume and number of transactions across the Lightning Network.
Basically just opening and closing of channel for lightning network and not it's off-chain transactions. Also on-chain transaction is on-chain transaction and it is more than that of PayPal and other payment processors.