My grandfather was in the US army around 1900 and IIRC the family was able to find a record of it.
I do not do it, but there might be some wisdom in loading your magazines of your CCW handgun with rubber gloves. I am not sure how effective that would be in keeping your DNA off of your ammo.I didn't know their was a LE investigatory "Opt Out" option with commercial genealogy companies. A bit odd that a person wold submit their sample when they have such concerns in the first place. The family relatives "frag pattern" with a DNA sample is impressively wide. I think it's great when they ID a suspect from cold cases. I'm wondering when google, amazon and social media will make DNA sampling a mandatory sign up/continued use requirement. That's about all they need to complete their data collection.