Cargo/freight shipping could be a prime target for a cleaner ammonia base fuel as most of the ships currently run dirty semi-processed petroleum, “bunker fuel”. It’s a hyper-cost sensitive market so without regulation I’d doubt ammonia would compete. Still it could be a feasible option to reduce pollution. Some Western countries might accept ammonia or similar diesel replacement, as it’d be a sort of natural tariff, but likely China would lobby hard against such a measure. There’s have to be a very strong push from a few nations, which I’ll doubt we’ll see anytime soon.