The Uniswap Wallet supports ERC-20 tokens on Ethereum, Polygon, Optimism and Arbitrum networks.
In can switch networks when selecting the token you would like to swap:
Select the “Swap” Icon.
Next, select the token you would like to swap.
When selecting the token, select the network drop down from the tokens page to choose the network you would like to swap on.
To learn how to swap tokens, visit the help center article: How to swap tokens in the Uniswap Wallet