From my brief search it looks like most edible jellyfish is sold heavily salted. Like higher than average beef jerky salty.
You'd need to change preservation techniques to really use jellyfish a lot of your daily protein intake.
Jellyfish: > Protein 6.67 g > Sodium, Na 2081 mg
https://fdc.nal.usda.gov/fdc-app.html#/food-details/396504/n...
> Beef jerky > Protein 33.2 g > Sodium, Na 2081 mg
> Those headed for the table have their tentacles cut off; it is their upper dome, dried and preserved in salt, which is used in cooking. These jellyfish arrive at the restaurant in stacks of parchment paper, doused in rock salt
https://www.theguardian.com/lifeandstyle/2006/jan/27/foodand...