hardhat-etherscan v3.0.0

This new major version includes one of our most requested features: the possibility to specify multiple API keys for the hardhat-etherscan plugin (#1448).

You can learn more here, but the bottom line is that you can now do this in your config:

etherscan: {
  apiKey: {
      mainnet: etherscanApiKey,
      rinkeby: etherscanApiKey,
      optimisticKovan: optimismEtherscanApiKey,
      polygonMumbai: polygonscanApiKey,
      arbitrumTestnet: arbiscanApiKey,
  }
}

Importantly, the name of these keys don't necessarily match the name of the network in your config. See the docs to learn which names need to be used for each chain.