Around 25% of transaction are thanks to VeriBlock. They actually have a tracker on their own website which will tell you, which you can see here: https://explore.veriblock.org/network-stats. See the bottom right of the 3x3 table, "PoP Bitcoin Pct". PoP stands for "Proof of Proof".

You can also see this by looking at the huge dip and recovery of ~80,000 in the daily number of transactions which occurred at the start and end of March: https://www.blockchain.com/charts/n-transactions. This coincided with Veriblock's testnet shutting down on 4th March, and their mainnet launching on 25th March.