So as a result of an extreme example of inefficient bureaucracy, one which is probably unique to the military, I have found myself in the fortunate position of being paid to effectively work 2-6 hours a week for the next 6-7 months. It was preceded by 6-7 months of 60-80+ hour work weeks, so I like to think it all balances out.
I graduated a few years ago with a degree in computer engineering, and I am now located in a small coastal city. If you were in my position, beside the obvious of relaxing, hobbies, etc, what would you do? I have considered trying to find a part time development role (it would be difficult though as I am effectively on-call for when those 2-6 hours are). Alternatively, I could pursue a side project to keep my technical skills sharp, but I can't think of any that call me. Any ideas?
Your situation is a bit different from my goals, but honestly if I had that opportunity, I'd be doing my best to explore the woods/mountains nearby in whatever way I can.
I also kind of agree with the "Learn German" comment - learning a non engineering skill that's also either practical or brings you joy is a great way to eat up time. I'm speak a few languages, but as I only regularly use English in my day-to-day life, just maintaining the other ones at a high skill level is a time consumer, though one I enjoy doing.