Lenovo ThinkPad X390 won’t boot while plugged in

[mato-z]

Hello. I’m using Lenovo ThinkPad X390 Yoga (model type: 20NN002NMC). I have been using dual boot of the preinstalled Windows 10 x64 and Linux. About 6 weeks ago, after updating the BIOS N2LET76W 1.75 (https://download.lenovo.com/pccbbs/mobiles/n2lur14w.txt) and the Intel Management Engine Firmware (12.0.67.1579), an issue arose. When I boot to Ubuntu 20.04.1 x64 (kernel 5.4.0-42-generic) using the Grub bootloader with active Secure Boot (fully supported), and then I turn the notebook off or restart it in Ubuntu, it won’t turn back on – it won’t POST, the screen is black, etc. After that time, I need to unplug the notebook from the power adapter, or remove it from the dock, and it will boot on battery. But it won’t boot while plugged in until it boots into Windows and is turned off/restart from it. After booting to Windows, it works fine while plugged in, until it is turned off in Ubuntu again.

It looks like a BIOS/Firmware error related to power management. I’m using the latest BIOS/Firmware updated via the official Lenovo software – Lenovo Vantage (1.76). Notebook was sent to Lenovo for repairs, the motherboard was replaced, yet the problem persists – hence thinking it’s BIOS/Firmware related. Lenovo claims it’s Ubuntu’s issue, even though the list it as officially supported (https://support.lenovo.com/sk/en/solutions/pd031426) and there refer me to the community. I have tried installed all available drivers and softwer provided from Ubuntu.

I need dual boot for work, the notebook is rendered useless without it. I bought it as it lists support at https://support.lenovo.com/sk/en/solutions/pd031426. Moreover everything used to work fine up to 6 weeks ago. Lenovo service nor an authorised repair shop could help me. Could anyone advice me, please?

The only obvious way is to downgrade BIOS, but it is not solution for me. Lenovo new bios releases are very often (for example 2 times/month) and it solving serious problems like problems with dock, security issues etc. Many thanks for your help.