In general, the easiest online brokers to start with are newer platforms designed for easy, everyday use. Apps like Robinhood and Webull were built with beginners in mind and aim to make trading accessible for anyone with any level of knowledge.
That said, it depends on what you need out of a broker. Bigger firms might seem more confusing to start but often come with a wider network of advisors, in-person help, and educational resources.
If you're looking for ease in terms of time commitment, you might want to look into a robo-advisor. That said, while these algorithm-based platforms do the leg work for you, they often come with lower earning potential than self-directed trading.