For me, it's the gauntlet quest. Even though it is replayable, it is still showing up in my quest log as the only one, and won't complete again. I'm stuck, unless that's all the content there is for now. I made it past Zakira's second quest. I have no new quests
Zakira's 2nd quest is the last of the Main quests, for now. Although I can't figure out why you keep seeing 'The Gauntlet' quest since it should disappear from the log after the second H scene with the blacksmith, so I'll take a look into that.
Other objectives, like recruiting the girls, don't appear in the log, though I could add them in a future update if it becomes difficult to keep track of all of them.