The Soviet Union's (in cooperation with some European governments like France and West Germany) Vega missions put balloons in the atmosphere of Venus back in 1985. It was 30 years ago, the last successful interplanetary mission of Soviet/Russia. There are advanced paper plans for airships in the atmosphere of Venus. But I've never heard of anything similar for Uranus or Neptune. I actually hear very little about any mission plan for Uranus or Neptune.
Would it be more difficult to put an airship in the atmosphere of the gas giants, compared to Venus? It is colder and another composition and probably another density profile, and overall less known. What difficulties would arise, and how might they be overcome? Would radio communication get difficult? I note that all three mentioned planets have about the same surface gravity, very similar to that on Earth (although "surface" might have a fuzzy definition on a gas giant). Of course it is much more difficult to get to Uranus, though its deeper gravity well and aerobraking helps, but I ask about what can be done with an airship once a probe has entered orbit there.
I want to add the side question if it would be valuable for exoplanet research to examine especially the atmospheres of Venus, Uranus, Neptune since the most common exoplanet size seems to lie between them, and their atmospheres might be analyzed with telescopes planned for the next few years or a decade. Is there a sensible synergy between studying those three planets here, and exoplanets?