Comment 15 for bug 1845289

Bug 1839317 looks too similar to ignore the possibility of the same underlying issue. There's other person there besides me who reports the same behavior on amd64.

My Windows bootloader is fine.
I can boot Windows using my motherboard's EFI boot menu selector.
I can boot Windows if I downgrade GRUB to the version from Ubuntu 19.04 (2.02+dfsg1-12ubuntu2).

My setup is EFI + GPT. Secure Boot is disabled.

Partitions:

Device Start End Sectors Size Type
/dev/sda1 2048 821247 819200 400M EFI System
/dev/sda2 821248 1083391 262144 128M Microsoft reserved
/dev/sda3 1083392 210209396 209126005 99.7G Microsoft basic data (WINDOWS 10 SYSTEM IS HERE)
/dev/sda4 210210816 211257343 1046528 511M Windows recovery environment
/dev/sda5 211257344 420513791 209256448 99.8G Microsoft basic data
/dev/sda6 420513792 445679615 25165824 12G Linux filesystem (UBUNTU ROOT, EXT4)
/dev/sda7 445679616 468860927 23181312 11.1G Linux filesystem (UBUNTU HOME, XFS)

Mounts:

/dev/sda1 on /boot/efi
/dev/sda6 on /
/dev/sda7 on /home

/etc/default/grub custom options:

GRUB_TIMEOUT=5
GRUB_CMDLINE_LINUX_DEFAULT="quiet systemd.show_status=1"
GRUB_GFXMODE=2560x1440
GRUB_DISABLE_RECOVERY="true"
GRUB_DISABLE_SUBMENU=y
GRUB_GFXPAYLOAD_LINUX=keep
GRUB_FONT=/boot/grub/terminus-32b.pf2

/etc/grub.d/30_os-prober renamed to /etc/grub.d/07_os-prober