I'm learning how to create erc20 tokens, and after adding liquidity to my token for test, I Renounced ownership and now my eth is stuck in Uniswap. Is there a way to remove the liquidity even as I'm no longer the contract owner?
You don't remove liquidity from a token unless the token is a pool contract. You can remove your liquidity from the pool as long as you still hold the pool tokens, to burn for the underlying tokens they represent.
You should first try to do that from the web interface if uncomfortable with calling contract directly.
If your token that is in the pool has some strange mechanic or was launched with faulty parameters such as token tax on transfer designed to work with a different router, it is possible you have locked the weth with them in the pool contract.