Is it possible the 22.04 install was setup using legacy dm-raid format? The legacy dm-raid format does not include a header so it looks like a raw ext2 to grub and it can "embed" there (as it will see the ext2 on either disk at boot).
Anyway, reassigning to subiquity for triaging. ** Also affects: subiquity Importance: Undecided Status: New ** Changed in: grub2 (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2060695 Title: 24.04 grub-pc cannot upgrade on mirrored software RAID root disk To manage notifications about this bug go to: https://bugs.launchpad.net/subiquity/+bug/2060695/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs