The short answer is that we do not support an F2FS /boot filesystem and support is not built into signed monolithic GRUB for that reason.
If you need to have an F2FS root partition, you can use a separate /boot with a supported file system as you suggested. If you insist on having F2FS as /boot, you will have to build your own GRUB image I am afraid. ** Changed in: grub2 (Ubuntu) Status: New => Won't Fix -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2098748 Title: GRUB issue. Kubuntu have not fully support F2FS file system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/2098748/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs