Is there anything currently in the game that has not been discovered/solved?

actually, does anyone know what that button underneath the waterfall near troms is for other than lighting that lamp

 

If you can figure out who wrote Finding Meaning (the Canary Calls) that's still unsolved. It's been confirmed that the pieces of the puzzle are all there and that it is possible to figure out who wrote it, but I guess no one's tried because I can't find anything about it.

 

If I had to make a guess maybe Grenot (old starting NPC for canary calls)? I'm most inclined to that since it is a callback to the old version of the quest and finding meaning's author's name is 6 characters.

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I am both very inclined but also doubtful that this is referring to Garvan running away on the rooftops when approached during the stage where you talk to people in the village.

Edit: upon looking at eua's dialogue (the villager without any name in that village) it might also be possible to interact with garvan outside of hollow serenity pre-completion?