So the Associated Press recently uploaded a massive archive of videos to Youtube. Great resource, I have always loved news video databases.
Anyways, search https://www.youtube.com/channel/UCHTK-2W11Vh1V4uwofOfR4w/search?query=natural+sound in the channel for it to list all the videos which contain just the microphone accompanying the filming. Lots of war and different news type stuff, but it’s so diverse I bet you could dig some really interesting samples out of there.