if you want to keep discussing this movie after Feb 20th IMDb shutdown

I recommend you to move to The Movie Database (TMDb) https://www.themoviedb.org, it's alternative to IMDB run since 2008. It's open database edited by its own users, you can export watchlist and rating list from IMDb and easily both import them to your TMDb account (you can actually also export all your boards posts from IMDb into one bug HTML file through Chrome browser extension, just search in Chrome store). And of course it has also discussions system for EACH movie or TV show, though discussions feature was launched just few days ago in response to IMDb boards closure, so don't expect much content there yet.

Here is page of Fantastic Beasts and Where to Find Them movie:
https://www.themoviedb.org/movie/259316-fantastic-beasts-and-where-to-find-them

And its discussions you can open by click on top left bubble icon or in the bottom of page next to Reviews or directly through this link:
https://www.themoviedb.org/movie/259316-fantastic-beasts-and-where-to-find-them/discuss

This site is real alternative with database of movies and TV shows and discussions specific for EACH movie or TV show, unlike useless forums which popped out in these days, only other place seem to be Trakt.tv with its comment system, though that is not very convenient and doesn't have much traction.