Why not? Weapons cannot be installed on hovercraft? They were in Vietnam granted maybe not heavy weapons but with drones, aircraft, missiles, light weight, rapid fire and heavy firepower weapons today I don’t see why not.
They work well on the ocean, beach, and other open areas, but they require an ungodly footprint for the weight they carry. A hovercraft APC, with ARMOR, would be insanely huge and not very maneuverable around trees, bushes, etc. They don’t turn on a dime, while a tracked or wheeled vehicle can pivot in place. Minor hits with small arms fire would degrade the lift skirts and cripple them. Not to mention the insane horsepower required to lift and move them.