Comment 1 for bug 1833107

This is almost certainly due to the grub2 package not adding the xfs filesystem module to the target /boot path; that was the original bug I filed. And Foundations pointed out that even if grub2 did fix this bug of copying in the needed fs modules, that it would break secure boot since , at least at the time, the xfs module is not signed like the ext4 module.

See this comment:

https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1652822/comments/3

so, if we wanted we could verify whether or not /boot in the target contains the xfs module and whether the grub.conf includes the insmod command.

And further, we could list what modules are provided in the secure-boot path and note whether or not xfs is in that collection of signed modules.