dell T20 immediately restarts after shut down

Hello,

I've got exactly the same problem as my Dell XPS 13 previsouly with my new Dell T20, firmware A11, Proxmox OS.

I've tried multiple solution given by various community (Dell, Ubuntu, Arch...):

• set acpi=force or acpi=noirq : NOT WORK
• install laptop-mode-tools: NOT WORK
• set SATA to Off -> ATA -> AHCI -> RAID: NOT WORK
• unpugg every USB device: NOT WORK
• set Power State to Disable / Only S5 / Only S4-S5: NOT WORK

As I manage my serve remotely, it is a serious issue for me, and as I see, Dell is not very carefull/serious with this kind of options.

Does anybody has another solution ? Maybe Dell will finally handle this feature correctly... 

Thanks