Installing an NMO mount on an aluminum body vehicle is no different than on a steel body vehicle.
Fire engines and ambulance bodies have been using aluminum for a long time.
I've done NMO installs on F-150's and F-350's.
The aluminum is a pretty hard type. It's harder to drill than steel body panels. Takes a bit more time, but not much. Just go slow with steady light pressure and let the hole saw do the work.
Galvanic corrosion is only an issue if you have water involved. A properly installed NMO mount will not let water anywhere near the bare aluminum.
Use quality mounts, no Tram/Browning/Amateur grade crap. Use Larsen, Laird, etc. Don't drill a hole in a $30-$40 thousand dollar truck and use the cheapest mount you can find. Use the right stuff.
Use the correct hole saw for the job. Aluminum isn't an issue, but you do want a suitable hole saw designed for drilling metal.
The NMO mount will come with an O-ring that goes under the outer ring. Before you install that, coat it with the grease that comes in the kit. That'll help prevent the O-ring from binding up as you tighten it down.
Tighten the outer ring snug, but don't go white knuckled on it.
Done correctly with the right tools, you will not have any issues.
Do periodically remove the antenna from the mount and clean underneath it.