SAVED GAME: link
1. Load the attached save.
2. Talk to Edér. If I picked the right save, this will be in Vilario's Rest next to the campfire and it'll be the first time initiating a conversation with Edér.
3. Observe that you can ask him three questions besides quitting the conversation; one of them is whether he likes the Deadfire.
4. Ask one of the other questions (not the Deadfire one.)
5. Once you exhaust that line of questioning and get back to the original dialog node, observe the option to inquire about the Deadfire is no longer present.
I believe the ability to ask about the Deadfire should not disappear if you pursue a different line of questioning first.