Farming seaweed is not that complicated and is pretty widespread.
> Today, seaweed makes up nearly 30 percent of the wet weight of all seafood produced by aquaculture globally. About half of cultivated seaweed is red algae and about half is brown; of the brown, most is kelp.
https://hakaimagazine.com/features/banking-on-the-seaweed-ru...
There's also a company called Running Tide "farming" seaweed explicitly and exclusively as a carbon sink technology. Kelp is grown on rafts until it gets heavy and sinks to the ocean floor where it nourishes micro- and macrobiota.
Dulse flakes, laver, kombu, and a few others are available from Maine Coast Sea Vegetables Inc., for one, and if Bren Smith (aquaculturist and author of Eat Like a Fish) has his way, there will be more and cheaper seaweed available soon. I've eaten seaweed since I was a kid (mom grew up near the ocean), and sometimes add a few strips to black beans in the InstantPot for the flavor (again, my mother's influence). My family doesn't seem to mind.
(For anyone else curious, short story is they're basically multicelular algae)