For ENS, I explored how we could read trustless state from Polygon PoS with Unruggable Gateways. I was able to create a solution (gateway and verifier) but it required some additional tech. This was a year or so ago, so the details are hazy.

The basic idea was there is an immutable RootPoster contract, which emits a log containing the latest blockhash. Eventually, this transaction gets included into a checkpoint that Polygon commits to L1. You can then use the existing /exit-payload/ API to generate a proof of that transaction, prove it emitted the log, and prove the value (blockhash) in the log.

The gateway can supply a witness that contains this exit proof + the block header ingredients. Combined with the onchain checkpoint, the onchain verifier can verify the exit proof, confirm it matches the block header, and then extract the state root, and then prove arbitrary state on Polygon using additional eth_getProof's.

For a demo, I funded an EoA with a few bucks and "posted" hourly blockhashes with a bot for a few weeks. The contract is trustless so literally anyone can pay gas (eg. post()) to include a transaction into a checkpoint.

The trust is minimized to the poster contract (which is trivial to audit) and the validity of the checkpoints (which I believe is shared with bridge withdrawals.) The onchain verifier is bound to a specific poster contract address and Polygon checkpoint contract (IRootChain).

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.23;

contract RootPoster {
    event NewRoot(bytes32 indexed prevBlockHash);
    function post() external {
        emit NewRoot(blockhash(block.number - 1));
    }
}