It's good to know that you're enjoying the game!
The latest update, v0.1.4, is already on Patreon, and you're welcome to continue the adventure.
Regarding your report:
The Gatekeeper's quest requires you to kill not three but ALL lava lurkers; once you do that, you get the on-screen message to return and finish the quest.
Even if you kill all lava lurkers BEFORE talking to the Gatekeeper, you'll still get all interactions with her, and after receiving her quest, just talk to her again, and the quest will be complete. You'll get another task from the Gatekeeper after that, and it'll take you to a new map. Hope this helps!