How about doing it manually instead of using the CLI tool to generate a key pair?
Have you heard that you can generate a key pair by using a coin?
If not, then it should be the best where you can randomly generate a unique private key from Coin Flipping.
We have a guide on the forum on how to do that check this link below
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https://bitcointalk.org/index.php?topic=3222335.0Once you've done generating a binary convert it to a hex and then use the bitaddress as suggested above and run it offline and convert the hex to the Wif key and public key.
WIF key should be supported to any wallet like Bitcoin core or Electrum.