Comment 1 for bug 1917509

On my local bare metal groovy install I tested upgrading to the new grub binaries from groovy-proposed and after a reboot my machine successfully booted - I have tried to generalise the instructions for doing this so they can be used on any release:

# enable use of -proposed as per https://wiki.ubuntu.com/Testing/EnableProposed
cat <<EOF | sudo tee /etc/apt/sources.list.d/ubuntu-$(lsb_release -cs)-proposed.list
# Enable Ubuntu proposed archive
deb http://archive.ubuntu.com/ubuntu/ $(lsb_release -cs)-proposed restricted main multiverse universe
EOF

# only selectively upgrade from -proposed
cat <<EOF | sudo tee /etc/apt/preferences.d/proposed-updates
# Configure apt to allow selective installs of packages from proposed
Package: *
Pin: release a=$(lsb_release -cs)-proposed
Pin-Priority: 400
EOF

# get list of packages in -proposed
sudo apt update

# update standard grub2 packages from -proposed
sudo apt install \
     grub-efi-amd64-bin/"$(lsb_release -cs)"-proposed \
     grub-efi-amd64-signed/"$(lsb_release -cs)"-proposed \
     grub2-common/"$(lsb_release -cs)"-proposed \
     grub-pc/"$(lsb_release -cs)"-proposed \
     grub-pc-bin/"$(lsb_release -cs)"-proposed \
     grub-common/"$(lsb_release -cs)"-proposed

sudo reboot