Concordium Node has been released for mainnet in version 4.1.1 . This is a major release that supports protocol version 4 that implements delegation and new smart contracts.
This is a mandatory update for all node runners on mainnet. The new protocol version will take effect next week at which point node version 3 will stop.
concordium-client
in version 4.0.3 and cargo-concordium
in version 2.0.1 remain valid as released previously.