Do JAG lawyers deal with patent laws, or is that something that they don’t really bother with?

It is possible to develop something is patentable while on active duty, if it meets the relevant legal conditions to be granted a patent. But the patent will likely belong to Uncle Sugar. In which case, JAG lawyers will step in to secure government rights to the patent. However, if it is developed by a retiree and you want to get it patented, JAG lawyers can advise you a bit, but that's it. They aren't patent lawyers, which is what you need. At least that's my theory. I'm no lawyer and I could be as wrong as a fat in church (which will help you maintain adequate social distancing).

Look JAG normally deals strictly with Military Issues ONLY. They don't do civilian cases, divorce, inheritance, etc. Best bet is to talk to them quick and see.

The vast majority of JAGs will never run into a Patent law issue. In the Army Acquisition organizations those issues come up enough that we have full time Army Civilians that handle that kind of law. A JAG can and do get stationed at a locations that deal with patents and work them but it's not a major part of their job.

I'm not a Lawyer