This I would associate with Prenormal … I thought I had done a rather overkill with the many links (or follow my links) to the Prenormal situation there.
Very loosely speaking Samsung would, on one hand, allow you to unlock and apply an official binary (first part of marine’s story) – but a Custom binary requires a further level of unlocking which is unavailable in the Prenormal state (his second hurdle).
That was way back in early 2022, different Android versions and I guess different install page now. It is mainly covered in the Pre-install instructions, Install /e/OS on a Samsung Galaxy S10e - “beyond0lte” perhaps tell us where you are at with reference to that ??