Hello,
Despite it happening in both operating systems I would be tempted to install a fresh dummy OS on a separate drive and see if the problem persists there. A failing PSU will often result in random rebooting rather than any system stalls or hangs, and they would be sporadic based on load, not repetitious.
Try installing a dummy OS and update the UEFI to the latest available version from the ASUS Support portal.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090