Where does the initial supply of an SPL token go if no mint authority is present?

Question

From the SPL code it says that the mint authority is optional and if its not provided, then the SPL token has a fixed supply. Which account is the recipient account of the fixed supply?

pub struct Mint {
    /// Optional authority used to mint new tokens. The mint authority may only be provided during
    /// mint creation. If no mint authority is present then the mint has a fixed supply and no
    /// further tokens may be minted.
    pub mint_authority: COption<Pubkey>,
    /// Total supply of tokens.
    pub supply: u64,
    /// Number of base 10 digits to the right of the decimal place.
    pub decimals: u8,
    /// Is `true` if this structure has been initialized
    pub is_initialized: bool,
    /// Optional authority to freeze token accounts.
    pub freeze_authority: COption<Pubkey>,
}

Answer 1

There is no actual supply until you mint it.

You would need to first create a token account and the mint to that account:

spl-token create-account EBF22st7gRqvKtEYW2WomsHUsNrjtPcZvpDAnh6W7Ugu
spl-token mint EBF22st7gRqvKtEYW2WomsHUsNrjtPcZvpDAnh6W7Ugu 100

You can set the mint authority to null and then you can't mint anymore. So its optional, but without it you cant mint anything.
You cant create a token without mint authority and it defaults to the client keypair that creates the token.