These two commands do not work on the newer wallet version.
Both commands are stricktly functional on a legacy wallet
as per the Console feedback error code -4
How about the dumpprivkey? it works for me my current Bitcoin core version is v26.0.0 the dumpwallet also does not work for me except for dumpprivkey it should work to you unless your wallet is encrypted with passphrase you will need to use the command below to unlock it first before you dump the private key
walletpassphrase "my passphrase" 60
If this does not work maybe you did disable the private key during wallet creation? or this is a descriptor wallet?
For the descriptor wallet, you can follow the guide from this link below on how to export private key it is a bit complicated compared to old ways to dump private keys.
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https://bitcointalk.org/index.php?topic=5449245.msg62109703#msg62109703