Well, the issue seems to have resolved itself, at least for the last couple of days.
No changes to configuration, no homeassistant updates, just removed and re-added the light a few times. The light continues to work, just doesn’t turn itself on at 6pm and 6am, at least for now. I’ll update if it comes back.
Did you experience anything like described again after the last time re-adding devices? I’m experiencing the same, random light starts, but this seems to be when someone arrives at home. No automation thought that this triggers in the logs, it’s just turned on.