I have a dual boot Win 10 - Ubuntu 16.04 on my PC and wanted to run Ubuntu after more than a year without using it. Choosing Ubuntu in the GRUB worked, but the initialisation process got stuck in the loading phase with the Ubuntu logo. This had already occurred in the past after major Win 10 updates and was usually fixed by running boot-repair from a live USB.

I tried running boot-repair from a live USB (Ubuntu 20.04) but it kept showing the following error :

Please create a ESP partition (>1MB, fat boot flag). This can be performed via tools such as Gparted. Then try again.

I wonder why this error appears as there is an EFI partition on sda2. More details: my boot-repair log file

Besides, I earlier managed to launch Ubuntu once by tapping e on the Ubuntu entry from the GRUB bootloader, and adding acpi=off at the end of the line linux ..., followed by CTRL+X (I assume this is more specific to my Lenovo Yoga 2 Pro laptop).
Unfortunately after rebooting I could not repeat that step, and the GRUB bootloader screen has now been replaced by a grub console...

Any help would be very much appreciated !

Kind regards,

Valentin