Block 566687 nonce with extranonce, how to interpret?
I can't find any code examples to try and find the nonce for a block using the extra nonce, rather than the usual examples that go to a maximum 32-bit unsigned integer as the nonce.


The nonce for the block remains unchanged. Since the extra nonce is part of the coinbase transaction, it modifies the merkle root, which is part of the block header. Thus, for each extra nonce, you get a unique merkle root, which then allows you to try the full range of regular nonces with that merkle root.

You do not need to concatenate or otherwise mix the two nonces in any form - the extra nonce's purpose is simply to alter the merkle root.

To validate a block with an extra nonce, you don't need to do anything special. Just build the transaction merkle tree, verify the merkle root matches the root in the block header, then hash the header and check it agains the target. It's the same process for blocks with and without the extra nonce.