I believe it had to do with the patch debian/patches/quick-boot-lvm.patch as described here: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1800722
Here's what I wrote in a comment (#12) there a couple days ago:
Seeing a regression here on 18.10/amd64 with 2.02+dfsg1-5ubuntu8.1 using EFI+btrfs boot volume. No LVM used, just GPT on NVMe.
Regardless of my settings in /etc/default/grub, the boot wait is now 30 seconds.
Relevant settings: GRUB_HIDDEN_TIMEOUT=1 GRUB_HIDDEN_TIMEOUT_QUIET=false GRUB_TIMEOUT=0
I've downgraded using the following commands: apt install grub-common=2.02+dfsg1-5ubuntu8 grub-efi-amd64=2.02+dfsg1-5ubuntu8 grub-efi-amd64-bin=2.02+dfsg1-5ubuntu8 grub2-common=2.02+dfsg1-5ubuntu8 apt-mark hold grub2-common grub-efi-amd64
And it's returned the previous behavior.
I believe it had to do with the patch debian/ patches/ quick-boot- lvm.patch as described here: https:/ /bugs.launchpad .net/ubuntu/ +source/ grub2/+ bug/1800722
Here's what I wrote in a comment (#12) there a couple days ago:
Seeing a regression here on 18.10/amd64 with 2.02+dfsg1- 5ubuntu8. 1 using EFI+btrfs boot volume. No LVM used, just GPT on NVMe.
Regardless of my settings in /etc/default/grub, the boot wait is now 30 seconds.
Relevant settings: TIMEOUT= 1 TIMEOUT_ QUIET=false
GRUB_HIDDEN_
GRUB_HIDDEN_
GRUB_TIMEOUT=0
I've downgraded using the following commands: 2.02+dfsg1- 5ubuntu8 grub-efi- amd64=2. 02+dfsg1- 5ubuntu8 grub-efi- amd64-bin= 2.02+dfsg1- 5ubuntu8 grub2-common= 2.02+dfsg1- 5ubuntu8
apt install grub-common=
apt-mark hold grub2-common grub-efi-amd64
And it's returned the previous behavior.