Is it fine to learn Vipassana meditation online? Is it essential to go to SN Goenka centre for 10 days to learn Vipassana? Or is it fine to learn Vipassana online?
Doing an intensive course at a dedicated meditation centre is incomparably better than online learning, but doing an online course or something similar is actually better in my opinion as a first step.

Often when people come to our centre having never practiced or having practiced a different tradition, they spend quite a bit of time becoming accustomed to the practice and accepting it. They waste a lot of time doubting and fumbling, and given they often have a limited number of vacation days it often makes finishing a foundation course difficult. 

Much of the doubt and fumbling is mitigated by online teachings - most people coming to our centre have little doubt and lots of practice based on static teachings they have found on the internet. Moreover, those meditators who have completed our online course (which just means they practiced at least an hour a day and we talked once a week, giving them new exercises weekly) veritably and invariably sail through the intensive course since they are very well prepared for it.

So, yes, online meditation is perfectly valid, but I think it serves better as a preparation, rather than a replacement, for intensive practice which is best done with a teacher at a centre.

You can check out https:/meditation.sirimangalo.org/ for our online course system. There are some testimonials you can read I think, but I can say myself the online courses have made a big difference in our community.