Uniswap is a decentralized protocol for automated liquidity provision on Ethereum. The keywords here are on Ethereum. UniSwap does not facilitate cross-chain swaps. If you want to swap between an ETH or an ERC20 token and a token on another chain... you can't. This is why UniSwap, and every other UniSwap clone and on-chain DEX need "wrapped" (a.k.a. "pegged") tokens, like wBTC, to represent an asset from one chain to another.