Desiccants aren't nearly effective enough to dehumidify something like a room. [EDIT: apparently desiccant dehumidifiers are a thing too, although much less common in the home consumer world, so never mind -- disregard this whole comment!]
The answer is #2. Air conditioning units and dehumidifier units, which are essentially the exact same thing except for where the hot air output goes. (AC's send the hot air outdoors; dehumidifiers mix it back with the now-dehumidified cold air.)
ACs don't send the hot air outside. They transfer the heat outside. They usually recirculate the inside air. But the act of running the inside air across the cooling coils causes water to condenser on the coils and thus dehumidifies the air as well.
If portable A/C units aren't sending the internal air outside, does that mean they're also just circulating outside air as a way to disperse the heat, rather than actually blowing air outside?
Some portable A/C units do send hot air outside, and some don't. The two-hose models AFAIK are the latter type (although the un-insulated hoses are wildly inefficient)
The answer is #2. Air conditioning units and dehumidifier units, which are essentially the exact same thing except for where the hot air output goes. (AC's send the hot air outdoors; dehumidifiers mix it back with the now-dehumidified cold air.)