I just left the Asylum (intending to go with Saemon) and Neera seems to be silent, even though when inside, enough time should have passed to trigger the next talk (I also tried using the C:AdvanceRealTime console command, it didn't get me a next one).

My last pre-Asylum talk was the one ending with Neera saying (roughly, I don't remember it word for word) "But I know what I want now. I want you." (and Neera's romance variable is still at "2").

Was that the last SoA talk, is there some extra talk condition other than time for the next one, or did I get stuck somehow?

I seem to remember (I could be wrong) that she won't talk whilst in the Underdark. Wait until you exit in chapter 6.

I meant that she said nothing after leaving Spellhold (so finding myself in Brynnlaw again, before going with Saemon), so not in Underdark yet.

Or does the next talk have some condition about being post-Underdark or so?

I see. When I last played SoA enhanced, the Neera romance was horribly bugged -- not to mention how irritating she is -- so I can't say for sure. Somebody may come along who's followed it through, assuming it isn't still buggy as hell.