According to official docs of ethers.js, this should be the way how to connect to a specific network like Rinkeby-testnet with custom data:
const provider = ethers.getDefaultProvider(network, {
etherscan: ETHERSCAN_API_KEY,
infura: INFURA_API_KEY,
Also, this would be the way to get a signer in order to sign transactions:
const signer = provider.getSigner()
However, there is now method "getSigner" available on the default provider.
TypeError: provider.getSigner is not a function
How to achieve that using ethers.js?