I withdrew some ETH from an exchange and picked Linea because the withdrawal fee was much lower. The coins arrived in MetaMask, but I now need to send them to a service that only accepts ETH on Ethereum mainnet. When I switch from Linea to Ethereum in the wallet, the balance disappears even though the address stays exactly the same. I didn’t realize the two networks kept separate balances. How do I get the ETH onto Ethereum so I can use it there?