At about 700 km below the cloud tops, where the gases start to liquefy under pressure, the pressure is estimated to be merely 700 bar, less than half of the pressure at the bottom of the Mariana trench. Earth-made cameras should have no trouble operating there, given an adequate enclosure. The temperature might be a problem, but I could not find any estimates for that depth.

We could certainly put a plane / balloon deep into the Jupiter atmosphere, if we were able to slow the arriving spacecraft to subsonic speeds in the atmosphere. Given that the low-Jupiter orbital velocity is 41 km/s, it's not an easy feat, even if the spacecraft brings enough reaction mass for a retro burn to slow down and insert itself to the low-Jupiter circular orbit.