This would be my recommendation.
I don’t go to movies very often these days, but even before I was trying to lose weight, I generally didn’t buy the overpriced food and drinks they sold there. Movie-house popcorn is nowhere near as good as home-popped, with real butter (I promise you, the oil they drizzle over it is not butter, at least not in the US).
It’s just a couple of hours of sitting - not-eating is the easy approach.
If you want something to nibble on that is kind of the same effect (greasy, buttery, salty fingers) - take a pat of butter and melt it in a cup. Add in your favorite raw nuts (pecans are good for this), sprinkle on some salt. Mix it up, or put in a plastic bag and shake it up to mix. You are not looking for a heavy coating of butter, just enough to help the salt adhere.
Clearly you would not want to sit there and eat some huge bag full of salted, buttered pecans, so just an ounce or two. To satisfy your nibbling urge.
Another option - if you have lost 38 kg so far - just eat the popcorn. As long as it is a once-in-a-while thing and doesn’t trigger some massive backslide into carb eating, you should be fine.