So, after nothing else worked, I decided to clean install. Previously I already did "Reset this PC" multiple times, but it did not help, and I really doubted that clean install would be any different. This time I clean installed Windows 11, removing all partitions, and installing drivers only through Windows Update (except Dell Power Manager) and restored all my previous apps. Now the laptop is finally sleeping! Even modern standby is working.
Hey, Since I bought my Dell XPS 9300, I never was able to get it to sleep properly, so as advised by many threads here I changed it to hibernate when closing the lid. The problem is, even hibernating the laptop drain its battery to zero causing me to loss all my work. Looking at sleep study, it has no idea what happen after it went to hibernation (unlike when it was sleeping) - [IMAGE] [IMAGE] Same with logs in Event Viewer - [IMAGE] I tried - It's really frustrating that such an expensive machine just can't sleep/hibernate, no matter what I try to do.  I simply just want to close my laptop, go to sleep and wake up and have all my apps open without keeping it connected to AC. Any help would be appreciated. Thanks!  
Dell XPS 9300 drain to zero while hibernating