What is the total supply of ETH released by Linea?

Why are there almost 1 billion ETH in Linea Mainnet message service contract?
What kind of economic model does Linea do

Linea uses Ether, bridged directly from Ethereum Mainnet, as its native currency. Any advertisements of an existing or imminent Linea token sale or drop are scams and users should be cautious to avoid these.