So, can you learn piano online with a reasonable degree of success? The answer has to be yes; you can. You have to be sure the type of lessons taken is right for you. A classical course will not suit you if you want to play a few pop songs with friends and sing.
Should you spend time at home and take one-to-one private lessons, and can afford them, then that would be a better method, especially if you wish to take exams. My online students take exams, but I am fully booked with these classes.
If cost is an issue or when you can be available varies, then taking online lessons could be the best way to learn piano.
Then you need to decide on a membership site such as this one, with several courses available and complete video support.