This is a rough POC to read and verify a Matic anchoring: https://github.com/lemoustachiste/verifiable-presentation/blob/vaultie-verification/matic-rpc/matic-rpc-eth.js
It’s been 3 years since I worked on that and it was again a proof of concept, so things might not work out of the box, however I’m quite confident the RPC reading didn’t change. The RPC function is actually coming from this one: https://github.com/blockchain-certificates/explorer-lookup/blob/master/src/explorers/rpc/ethereum.ts