My fiddle leaf fig is about to hit the ceiling. What would you do?

If you want to keep it shorter, topping it is a reasonable option. Pick the height you want and make the cut just above a leaf node. New growth may appear below the cut, sometimes with more than one branch, so it can fill out rather than stay as a bare trunk.

You can try rooting the removed top as a cutting too, though it’s a separate project. The plant can grow upward again from a new shoot, so topping controls its height for now rather than setting a permanent limit.

I’d decide how tall you actually want it, then prune back to that point rather than taking off a huge amount just because it’s near the ceiling. If it’s healthy and actively growing, it may respond with new branches, but the shape afterward can be a little unpredictable. Keep a stake in place if the new growth makes it lean.

Honestly, you don’t have to cut it unless the height is a problem for you. But if it’s going to press into the ceiling, I’d top it. A big leafy top is also worth trying to propagate, so the pruning doesn’t have to feel like a total loss.