A mainstream one like https://www.investopedia.com/simulator/ https://www.investopedia.com/simulator/ could be an option. This one https://www.quantopian.com/

A mainstream one like https://www.investopedia.com/simulator/ https://www.investopedia.com/simulator/ could be an option. This one https://www.quantopian.com/ https://www.quantopian.com/ is also interesting. It's more algorithmic trading, but has backtesting functionality and other nice features.