On a focal system all up-to-date, I installed these updates (and only these) from focal-proposed, and everything seems fine. System is booting as normal.
grub-common/focal-proposed 2.04-1ubuntu26.11 amd64 [upgradable from: 2.04-1ubuntu26.9] grub-efi-amd64-bin/focal-proposed 2.04-1ubuntu42 amd64 [upgradable from: 2.04-1ubuntu26.9] grub-efi-amd64-signed/focal-proposed 1.164+2.04-1ubuntu42 amd64 [upgradable from: 1.142.11+2.04-1ubuntu26.9] grub-efi-amd64/focal-proposed 2.04-1ubuntu42 amd64 [upgradable from: 2.04-1ubuntu26.9] grub2-common/focal-proposed 2.04-1ubuntu26.11 amd64 [upgradable from: 2.04-1ubuntu26.9]
On a focal system all up-to-date, I installed these updates (and only these) from focal-proposed, and everything seems fine. System is booting as normal.
grub-common/ focal-proposed 2.04-1ubuntu26.11 amd64 [upgradable from: 2.04-1ubuntu26.9] amd64-bin/ focal-proposed 2.04-1ubuntu42 amd64 [upgradable from: 2.04-1ubuntu26.9] amd64-signed/ focal-proposed 1.164+2. 04-1ubuntu42 amd64 [upgradable from: 1.142.11+ 2.04-1ubuntu26. 9] amd64/focal- proposed 2.04-1ubuntu42 amd64 [upgradable from: 2.04-1ubuntu26.9] focal-proposed 2.04-1ubuntu26.11 amd64 [upgradable from: 2.04-1ubuntu26.9]
grub-efi-
grub-efi-
grub-efi-
grub2-common/