Comment # 19 on bug 1156441 from Michael Chang

(In reply to Ignaz Forster from comment #17)
> In bug 1126900, comment 14 I may have found a solution to mitigate the
> read-only root file system specific problem mentioned in comment 4: Linking
> the grubenv file to a writable subvolume would make it possible to write the
> 'env_block' variable when calling grub2-editenv.

Would you please provide more detail as it sounds the grub2-install should now
create symlink to the grubenv in writable subvoulume rather than regular file
as plain /boot/grub2/grubenv ? 

> 
> However this approach also doesn't solve the problem that GRUB is not able
> to write an environment variable until grub2-editenv has been called from
> userspace at least once.

Would you please check comment#18 for the test package ? IIUC you are also
looking for the $env_block to be initialized by grub2-install that the bug
report is all about, despite the regular file vs symlink not yet clear to me.

Thanks.