Well known problem, but unknown solution (at least so far). The question has been asked millions of times, but a solution to this specific case didn't show up while searching. Feel free to point me to an existing answer and mark this question as duplicate instead of writing a new one.
I installed Windows 10 in a new computer and then (in that order) OpenSUSE Leap 15.5. Just after the installation of Leap I got the OpenSUSE boot manager and booted into it with success. Then I wanted to finish up the installation of Windows and I started it. Note that I just started it and installed some drivers and some software (Thunderbird, VLC, Audacity, etc.). I didn't do any update (it may have done it behind my back, though).
Now when I boot I get thrown into the grub console with the few commands available and I'm not expert enough to know what to do there (1).
I inserted the OpenSUSE USB and booted from that, then at the menu I selected "rescue system". After loading all it has to load, I got into a root console and started trying to mount the directories of the installed Leap into /mnt in order to chroot into it (following the instructions in this answer). It is worth mentioning that the / partition in Leap is in a btrfs file system, if that makes any difference.
When I get to chroot /mnt I get the error "Bus error (core dumped)". I have no idea what that could mean and how to fix it.
I tried, following the instruction in the answer here, to directly tell grub2-install where to install grub, trying both with the efi partition mounted into /mnt/boot/efi and directly into the /dev/nvme0n1p4 device. None of them works. I get in both cases the error "grub2-install: error: failed to get canonical path for 'tmpfs' ". Notice that in the rescue Leap there is no update-grub command.
(1) While I was writing this question, this other popped up among the suggestions and I did try the commands shown there while in the grub prompt (obviously adapted to my system). They didn't work either: I still get thrown into the grub console without getting any menu with any choice.
If I select the Windows boot from the boot-order in the UEFI, Windows boots fine. I'm very out of ideas.
While I had the /boot/efi partition mounted, I noticed that in there there are the directories EFI, System Volume Information and some other stuff I forgot, as well as the file BackupSbb.bin. This leads me to believe that Windows did it's own stuff in the efi-partition, which leads me to the next, and possibly most important, question: is there anything the world can do to protect itself from the despotism of Microsoft (read, to prevent it from happening every time)?
