In terms of the Russo-Ukrainian War, NATO has eyes-in-the-sky basically all the time, both for intel support to Ukraine and to monitor the war itself for future warfighting lessons.

Separately, troops from several countries have been confirmed to have been in Ukrainian territory during the war in a training capacity. Unironically, they probably are there in a non-combat capacity simply because the gain of a few NATO troops isn’t worth the risk of exposing them to combat, but I expect that the information stream there goes both ways.

NATO brass has also confirmed numerous discussions with the Ukrainian brass on the course of the war, and I would have to imagine that includes the technology and tactics developing and not just the position of the front lines.