Two passages. First:
Moses’ father-in-law said to him, “What you are doing is not good. You and the people with you will certainly wear yourselves out, for the thing is too heavy for you. You are not able to do it alone. Now obey my voice; I will give you advice, and G-d be with you! You shall represent the people before G-d and bring their cases to G-d, and you shall warn them about the statutes and the laws, and make them know the way in which they must walk and what they must do. Moreover, look for able men from all the people, men who fear God, who are trustworthy and hate a bribe, and place such men over the people as chiefs of thousands, of hundreds, of fifties, and of tens. And let them judge the people at all times. Every great matter they shall bring to you, but any small matter they shall decide themselves. So it will be easier for you, and they will bear the burden with you. If you do this, G-d will direct you, you will be able to endure, and all this people also will go to their place in peace.”Ex. 18:17–23 ESV
And second, a smattering of verses:
In the second year of the reign of Nebuchadnezzar, Nebuchadnezzar had dreams; his spirit was troubled, and his sleep left him.
Daniel’s reply: “but there is a G-d in heaven who reveals mysteries, and he has made known to King Nebuchadnezzar what will be in the latter days. Yor dream and the visions of your head as you lay in bed are these:”
“At the end of the days I, Nebuchadnezzar, lifted my eyes to heaven, and my reason returned to me, and I blessed the Most High, and praised and honored him who lives forever, for his dominion is an everlasting dominion, and his kingdom endures from generation to generation;”Daniel 2:1, 28; 4:34 ESV
Jethro, as priest of Midian was not likely converted to following the L-rd all at once, though he did offer sacrifices to Him in some sort of recognition. Nebuchadnezzar certainly was not a follower of the L-rd, and during the time he was not following the L-rd, he received dreams and visions from the L-rd and at some point was humbled by the L-rd.
And from both of their lips and minds came insight and counsel.
Same with Cyrus, et al.
What I am saying is this. All truth is G-d’s truth, no matter where it is found. And we are wisest when we are hunting for truth, and it is my opinion that we do two things:
1) Hunt for truth.
2) Do so with a filter in place.
Just because someone is a pagan or an unbeliever does not mean they cannot utter the principles or a deposit of the truth of G-d from their mouths.
Further, just because someone has uttered a statement that is absolutely true does not mean their heart is fully yielded at all times to the King. Gifts, design, hardwiring, and intended function are irrevocable and without repentance. Being personally yielded to the King is a choice beyond walking in your function.
Further, just because we listen to one person at one point in one issue does not make that person a servant of the King, nor does it mean that He approves of all of their actions.
Further, as we parse things out and utilize truth (as I do, for example, with Marvel movies and Disney movies) we should readily understand that the propagation of those truths as a wholesale endorsement of the one speaking.
tl;dr G-d can use anyone, and His use is not necessarily the same thing as His approval.