Yes but I am not talking about how science or morality work. This is about how logic works. I am not saying we prove morals the same way we prove scientific facts. I am saying if objective morals are real/true then these truths or facts can be seens like Math or science facts. But I am not saying they work like science facts in that they are physical objectives but rather abstract objectives.
So therefore I am applying your logic that "moral truths changing means no moral truths" to science in that "science facts have changed so therefore theres no scientific facts.
I have and it doesn't necessitate a Divine authority. We can reason that moral principles are truths or laws that stand indenpdent of human views which gives them authority for all morally conscious and rational beings.
As free agents we can ignore that authority like we do the authority of the legal law or any Divine entity but that doesn't mean it they have no authority. If God is true and was the moral Authority as free agents we can defy Him so there is no magic force than forces us to obey moral laws.
Generally we give morals their authority through norms, laws and Rights. So we are more or less subjecting ourselves to the Authority of the moral truth prinicples that underpin norms, Rights and the laws.
Moral Authority
Moral authority is authority premised on principles, or fundamental truths, which are independent of written, or positive, laws. As such, moral authority necessitates the existence of and adherence to truth. Because truth does not change, the principles of moral authority are immutable or unchangeable, although as applied to individual circumstances the dictates of moral authority for action may vary due to the exigencies of human life. These principles, which can be of metaphysical or religious nature, are considered normative for behavior, whether they are or are not also embodied in written laws,[1] and even if the community is ignoring or violating them.[2] Therefore, the authoritativeness or force of moral authority is applied to the conscience of each individual, who is free to act according to or against its dictates.
Moral authority has thus also been defined as the "fundamental assumptions that guide our perceptions of the world".[3]
Moral authority - Wikipedia