Comment 3 for bug 2002085

Many thanks for sharing Jonathan.

Maybe we have a different curtin version, as on my side changes are effective with your patch in the snap environment but I am still getting the same error.

By checking the failing command, it looks like it is executed directly from target install... Which is not patched:

unshare --fork --pid -- chroot /target /usr/lib/grub/grub-multi-install

I may be wrong but I didn't found any way to patch it into target as early and post commands can't help us with that.