Hydrogen exploding may not be such a bad quality in this use case. It would be difficult for an aggressor party to get the drone back in one piece; snipers would be ineffective. A sniper could still take out the floating server, but (properly designed) the resulting explosion would wipe away any useful evidence of the server's purpose. One would likely need another drone built to separate the server from the balloon without aggravating the hydrogen.
Sadly (or happily), hydrogen doesn't explode that easily. The hydrogen autoignition temperature is 500 degrees Celsius. Even if a bullet were to effectively transfer heat, it's still 100 of degrees to cold. Hydrogen got a bad reputation from Hindenburg. It's irresponsible to use only because so many lives depend on it but still relatively safe. The first airship to circumnavigate the globe was a hydrogen zeppelin! And it never spontaneously combusted during its 12 year life apparently.
