I'm also in the same boat. 27 hrs in and was wondering why I could progress romantically with other characters but not Lucanis. I found this thread, checked it, and bidding farewell is missing from my completed quests list. It doesn't even show up as failed.
I also saved Treviso knowing that lock-out was possible so I'm disappointed that this bug happened anyway, but I will try repairing the game, maybe going back, and see what happens...
I’m so confused, it feels like romancing Lucanis is nearly impossible. Really challenging.
