Etherscan's V2 API at https://api.etherscan.io/v2/api covers Ethereum and dozens of EVM chains with one key; chainid picks the chain (1 is Ethereum mainnet). Errors come back as HTTP 200 with status "0".
Create a free key at etherscan.io and pass it as apikey. In the examples it's written {{ETHERSCAN_API_KEY}}.
Full reference: https://docs.etherscan.io/
In wei. The address is the Ethereum Foundation's.
curl "https://api.etherscan.io/v2/api?chainid=1&module=account&action=balance&address=0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe&tag=latest&apikey={{ETHERSCAN_API_KEY}}"curl "https://api.etherscan.io/v2/api?chainid=1&module=gastracker&action=gasoracle&apikey={{ETHERSCAN_API_KEY}}"