It isn't easy to solve it completely, but there are some things that you can do to minimize it. A simple periodic vinegar flush isn't going to do much.
Peggie Hall who owned a marine sanitation company and wrote a book on the subject says that flushing extensively after each use is the best way. Uric acid in urine reacts with calcium and magnesium in sea water and causes a white substance to precipitate out. Those white crystals combine with, you know what to form the scale on the insides of the hose. Flushing completely moves the problem to the waste tank, not the hoses.
Of course your holding tank fills up faster.
Removing the scale with chemicals, even strong hydrochloric acid is tough. You are better off removing the hose, replacing it or beating it against a tree trunk to break up the scale.
And even though I am not a chemist, I am a retired chemical engineer, so close.