It's my first posting here since this is the first time I run out of ideas regarding my computer with openSUSE Leap 15.4.
I did already a repair of grub2 on a ext4-filesystem successfully, but I have real trouble to do it on btrfs-filesystem.
Despite I followed the instructions from [URL="https://www.linuxquestions.org/questions/suse-opensuse-60/grub-not-load-after-a-power-fault-during-an-update-4175714484/"] (except the optional steps under point 3) I'm not able to chroot due to error
The complete btrfs-filesystem I mounted to .
Thera are following subvolumes on btrfs (from output of ):

• @
• @/var
• @/usr/local
• @/tmp
• @/srv
• @/root
• @/opt
• @/boot/grub2/x86_64-efi
• @/boot/grub2/i386-pc

To boot into Win11 is still possible, recommended configuration for UEFI regarding dual boot (f.e. disable fast boot) had been set.
Are there further mounts or bindings needed and if so, which I have to include?
Now I hope for good ideas from the community and say thanks for all in advance.

The good news is you shouldn't have made things worse. The better news is you probably don't need to do anything to Linux/grub.

Windows updates typically only change the default boot target - get into the machines setup screens and choose SUSe to boot. If that works ok, simply made it the default from the setup screens.

Thank you syg00 for your answer. The boot order in UEFI-Setup remained unchanged after the Win11-update.
I tried to play with secure boot (I assume you meant that with "machine setup sscreens"): if enabled windows bootloader startet as excepted, if disabled grub2 startet with the known menu. But neither opensuse standard nor a snapshot booted (choosing windows did work!), both run in an error. The same behavior when choosing opensuse from UEFI-bootmenu:
Did I get this error by chance while first boot after Win11-update? The output of "journalctl -xb" was only confusing to me. Yes, I have to get more familiar with btrfs.
So my first thinking of a demaged grub wasn't the right way, was it? My mind was set for it due to earlier experience with Win10 on a different machine.
Meanwhile I did a new installation in a new partition because I need the machine tomorrow morning working. Luckily I have all my data etc. in separate partitions. Not to much work but annoying anyway.
But there are still questions left:
Why I can't chroot in rescue mode?
Did the Win11-update demaged partially btrfs or a certain grub2-file?
What is to be done after following Win11-updates and I really expect trouble again?
I'd like to be prepared ...

To get a list of boot managers and which one is set to boot first try running the command

sudo efibootmgr

That will list which OS is set to boot first

Most likely not. The windows update may have changed the boot-order in the firmware/bios, re-enabled fastboot secureboot, or added another partition causing the drive partition order/table to change.

I checked UEFEI-setting, it remained unchanged.
As mentioned above windows bootloader did work with secure boot enabled and I got the grub-menu with disabled secure boot.
But both linux-entries (opensuse and snapshots) didn't work after the windows update.
I still don't have an idea why it happened and how to fix it except a new installation of opensuse. So my concern over following windows update is still alive.
For the moment I did the new installation as a workaround.