on my Dell XPS 13" with UEFI "bios", I installed Ubuntu 18.04 some time ago as dualboot with preinstalled Windows 10. Back then I had to enable Legacy boot, resized the partition with gparted and everything went was fine.
Today I wanted to reinstall Windows 10, so I proceeded to installer, but it complained something about GPT and refused to install (sth like this but little different message).
The next - BAD - idea was to delete all the Windows related partitions through Win installer, and create a new one. It also didnt work. But i dont care if my Win works, so I wanted to make ubuntu bootable again. Boot prompt said just
error: no such partition Entering rescue mode... grub rescue>
(hd0) (hd0,gpt4) (hd0,gpt3) (hd0,gpt2) (hd0,gpt1).
ls (hd0,gpt4) got
Filesystem is ext2 which was not true. Other partitions were unknown.
I had used grub-install several years ago, so I was pretty confident. But unfortunately
grub-install /dev/sd<Tab> didnt give any results. I realized that GPT and nvme would be the problem.
sudo grub-install /dev/nvme0n1p1 didnt help and gparted said my linux partions were unreadable. And
sudo update-grub got
Failed to get canonical path of /cow.