Keyframe intervals in OBS are just "keyframe per x seconds"; x264 itself exposes this as keyframe x frames. As I said in my comment, a keyframe interval of 10

Keyframe intervals in OBS are just "keyframe per x seconds"; x264 itself exposes this as keyframe x frames. As I said in my comment, a keyframe interval of 10 is doable. Don't be afraid of trying large values to see what they do.