So I was enabling some new Windows Security settings in Windows 11. What could go wrong, right? One of them was Microsoft Defender System Guard and it apparently disables S3 sleep mode. It took me half a day to troubleshoot as there's lack of any info on it. I even thought that sleep mode was disabled because of Hyper-V or WSL2, but I've had that for ages. Lots of misleading info everywhere, sadly.