What is Ethereum max supply?

Ethereum max supply is not a fixed number. The total supply of Ether, Ethereum's native token, is determined by various factors including the initial presale allocation, block mining rewards, and uncle/aunt rewards. However, the issuance of Ether is capped at 18 million per year, which means the relative inflation decreases annually. There's no theoretical maximum supply, but the rate of new tokens created will eventually reach an equilibrium with the average amount lost yearly due to various reasons.