In the USA, some of the states gambling is illegal. River boats and cruise boats allow gambling because vessels in open water are subject to federal not state law. Applying this logic to aircraft, would a Zeppelin have these same freedoms to allow gambling even if loitering over a state that prohibits gambling?
Short answer, No.
In the United State, all aircraft (even of other countries) may not have gambling devices onboard under title 49 SS 41311
An air carrier or foreign air carrier may not install, transport, or operate, or permit the use of, any gambling device onboard an aircraft
In Russia, gambling was banned in almost every part of Russia in 2009 expect for in the regions of Altai, Krasnodar, Kaliningrad, and Primorsky although I couldn't find any Russian laws against gambling on aircraft, it should be assumed that Russia would enforce its gambling laws on aircraft in its airspace.
In the UK, there are no laws against onboard gambling, it actually seems as if there are quite a few onboard gambling planes that are in operations.
In China, due to the structure of China's government, China has by far the most restrictions on what it's citizens can do in the country and abroad. Yes, you read that right China can and has punished citizens for breaking China's law in other countries (e.g. China's social credit system). source
gambling in china is illegal under Article 303 of the Criminal Law of the PRC (Criminal Law) (as amended in 1997).
To address the underlying question of "can countries laws apply to the airspace above that country" the answer is yes, airspace isn't the same as international waters. though it could be argued that the government's laws shouldn't apply to the skies as international-law scholar Paul Fauchille did, it has been applied case after case that US law applies to the airspace above the US.