Spoilers!
How do I progress beyond discovering that Ned is a mimic?
Sorry for not seeing this earlier. In case you still haven't found the answer:
You probably have to either talk to Silva or figure out how to solve Clevin's riddle (If you got Sal's event, than it's guaranteed to be possible, just pay attention to what they say, and to their appearance).
If you've done both than just talk to Untitled.