https://www.sciencefocus.com/planet-earth/what-would-happen-if-all-the-salt-in-the-oceans-suddenly-disappeared

I hate these takes, because they always open with "What would happen if a large volume of matter vanish?!" And yes, removing anything on the scale of "All the salt in all the oceans instantaneously" would be catastrophic entirely on the grounds that any instant movement of enormous mass is going to destabilize natural systems.

But the question that people are looking to answer is "What would the world look like if the Atlantic was a bigger version of Lake Michigan?" Not "what would hitting the oceans with a Star Trek teleporter do?"

https://worldbuilding.stackexchange.com/questions/50834/what-if-the-oceans-salt-level-decreased-by-50

Kinda grazes at the edges of this, but doesn't really seek to distinguish what a fully-desalinated ocean system would look like relative to a salty one. It just describes a transitional period in which freshwater life migrates out to the ocean. But it doesn't discuss what a deep-sea fresh water world would look like.

Also, the "eventually the sea would re-salinate" gets us to a more fundamental question "Why is the sea salty to begin with?" And that gives us insight into where salts come from and why they are fundamental to the ocean ecosystem.