Yeah that seems to be the latest kernel bug. So you couldn’t boot even with linux-lts or hardend?
That’s extremely strage . People had this same issue on forum and chrooting with live USB and reinstalling grub fixed it for them all without fail. Can you try to chroot just once more following this article.
If all that fails again. You could try this from grub rescue as last resort. Though this article is for ext file system translating it to btrfs shouldn’t be hard.
. People had this same issue on forum and chrooting with live USB and reinstalling grub fixed it for them all without fail. Can you try to chroot just once more following this article.