I still have a subscription to the Associated Press stylebook, and today I got an email with an update on Lake Ontario, which says in part:
"Trump's order only affects how the United States government refers to the body of water."
"Lake Ontario has carried that name for more than 400 years. Refer to it by its original name. If it is relevant to the story, acknowledge and explain the name Trump has chosen."
Way to go, AP! And not surprising, since the AP issued a similar statement about the Gulf of Mexico.