Section 1. Purpose. United States policy on civilian casualties resulting from U.S. operations involving the use of force in armed conflict or in the exercise of the Nation's inherent right of self-defense is based on our national interests, our values, and our legal obligations. As a Nation, we are steadfastly committed to complying with our obligations under the law of armed conflict, including those that address the protection of civilians, such as the fundamental principles of necessity, humanity, distinction, and proportionality.

So, this would be civilians in say Afghanistan, Iraq, or some other place where US military is operating. And really it says nothing about authorizing force against them, it's actually saying "we need further training to make sure civilians remain safe"

The U.S. Government shall maintain and promote best practices that reduce the likelihood of civilian casualties, take appropriate steps when such casualties occur, and draw lessons from our operations to further enhance the protection of civilians.

This is not really a weird executive order. It is probably just a response to the "accidental" bombing of the Doctors Without Borders hospitals the US did. I can find nothing in the Order that authorizes US military action on US soil.

Sites like the one OP linked to should be avoided as they are actively disseminating misinformation.