What the absolute fuck is canonical doing?!??!
“In 26.10, we’d like to propose removing the following features from signed GRUB builds:
Filesystems
Remove btrfs, hfsplus, xfs, zfs
Retain ext4, fat, iso9660 (and squashfs for snaps)
Image formats:
Remove jpeg, png
Retain none
We do not use images, but using that in your grub.cfg locally is a massive security risk (if even still allowed)
Partition tables:
Remove part_apple
Retain part_gpt and part_msod
Support for LVM
Support for md-raid; except raid1.
Support for LUKS-encrypted disks
In effect systems must boot with /boot on a raw ext4 partition (whether a separate or inside of /); on GPT or MBR disks.
This means for example, that an encrypted system must use an ext4 /boot partition; it is no longer possible to encrypt the /boot partition. Likewise a system on ZFS, XFS, BTRFS must use an ext4 /boot partition.”