EndeavourOS bootloader missing after BIOS update (dual boot)

Boot0000* Windows Boot Manager	HD(1,GPT,f1797e56-6e5f-cc45-a181-5c28a92c9a26,0x1000,0x1f4000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)
Boot0004* Windows Boot Manager	HD(1,GPT,a4ae3479-23b6-4c85-9ed4-9c9215776599,0x800,0x82000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)

Indeed it looks like that the BIOS update has wiped out the EFI boot entry for EnOS and somehow created a second Windows Boot Manager. Or the second WBM is the remnant of a previous Windows installation since it appears to be on the same disk and partition but different PARTUUID.

First, let’s see if we can create a new boot entry for EnOS.

Judging by the size of the ESP on your Linux disk, I suppose you are using systemd-boot and not Grub.

If systemd-boot, please follow the following instructions: In the live session

sudo mount /dev/nvme0n1p2 /mnt
sudo mount /dev/nvme0n1p1 /mnt/efi
sudo arch-chroot /mnt

Now in chroot:

bootctl install

Next type exit followed by enter to quit chroot.

Check with efibootmgr to see if a new EFI boot entry for Linux has been created.

If it is first in the boot order then fine. If not, go into BIOS settings and give it first boot priority.

It’s possible to use efibootmgr as well to change the boot order:

sudo efibootmgr -o xxxx,yyyy,zzzz ..... replacing the letters by the actual boot numbers.

If you are using Grub, let me know to give you the relevant command lines.

Also, it would be good to see the output of

sudo blkid