You can build a simple desalinator (aka, a solar still) with a couple bins, some glass/plexiglass, and access to sunlight. Preferably in an enclosed system to better contain heat and prevent water vapor from escaping.
No filters to replace, and it will run for as long as you feed it water.
Best link I could find to explain the process: https://www.intechopen.com/chapters/61215
Even putting it back into the ocean isn’t simple. If you do it in one big batch, you would kill everything in that location for a while. If you do it slowly, that isn’t simple.
Make margaritas. Put some on your steak. Throw the rest back in the ocean if you want.
We're talking, maybe a couple pounds of salt per person per day. It's not an unmanageable amount.
You're not going to hurt the ocean by adding back a little salt - salt that you took out of it...
Yes, you will most likely affect cultures within the immediate vicinity of a salt dump site but they will regrow elsewhere. It's peanuts compared to the amount of dilution being caused all the time by normal freshwater runoff and ice cap melts.
The ocean is very large.