It very much depends
Different franchises handle this very differently. For a brief survey of things I personally know about:
- Star Trek considers the films and TV shows to be a single shared continuity, but licensed works are usually thought of as having a lower level of canonicity, if not ignored outright.
- Stargate's continuity includes the TV shows, and the film is widely ignored.
- Star Wars semi-recently dropped from canonicity almost its entire expanded universe, and rebranded it as "Star Wars Legends." Prior to this restructuring, the franchise had an elaborate hierarchy classifying works into different levels of canon.
- Harry Potter's films clearly take place in a separate continuity from its books.
- Mass Effect's licensed works take great pains to avoid contradicting possible player choices, leaving them on arguably equal footing with the games. An entire story arc is established in a series of licensed novels before being casually referenced in Mass Effect 3 with no other explanation or setup.
- Dragon Age, on the other hand, deliberately does not do this, so its licensed works are clearly set in a more specific continuity than the games.
So, just as an example, we could choose to dupe questions like this:
- Star Trek: Allow duping questions about different series against each other, or questions about the TV shows and the movies. Forbid duping questions about licensed works against canon stuff or vice-versa.
- Stargate: Probably not an issue since most questions are about the TV shows anyway.
- Star Wars: Same deal as with Star Trek, but a different division of labor: canon on one side, Legends on the other.
- Harry Potter: Again, forbid duping books against movies or vice-versa.
- Mass Effect: This is harder because we don't have a formal canon policy from Bioware, to my knowledge. I would lean towards lumping everything together.
- Dragon Age: Questions about the licensed continuity are more specific than questions about the "main" continuity. The licensed continuity can be thought of as one possible path through the games. Allow duping in either direction accordingly, but only to the extent that the questions really are exact duplicates.
I am not actually proposing any of the above as formal policies; please do not cite this answer with respect to any of the above franchises.
The above list is intended to illustrate that every franchise will require a different treatment, and there is no one-size-fits-all answer to this question as asked. I would encourage close-voters and moderators to think carefully about these kinds of dupes, and to exercise common sense. If two questions are clearly "about" the same thing, and they will clearly have the same answers, they should probably be duped. If not, they should probably remain separate.