Package: grub2-common Version: 2.04-9 Followup-For: Bug #945404 The reason is lack of LUKS2 support. Specifically, in grub-core/osdep/devmapper/getroot.c, grub_util_get_dm_abstraction() has:
if (strncmp (uuid, "CRYPT-LUKS1-", 12) == 0) { grub_free (uuid); return GRUB_DEV_ABSTRACTION_LUKS; } That will not match LUKS2-encrypted volumes, so grub-probe thinks the filesystem will be readable. Although grub upstream has some LUKS2 support now (see https://savannah.gnu.org/bugs/?55093), that does not seem to cover this part of the code yet.