I am having a bit similar issue... like this: https://www.reddit.com/r/voidlinux/comments/ah86ac/stuck_on_executing_postinstall_kernel_hook_50grub/

I can't properly update my grub after taking LVM snapshot...

sudo modprobe dm-snapshot
sudo lvcreate -L 50G -n snap1 -s /dev/linuxvg/rootfs
Warning: Monitoring failed on snap1
Warning: Monitoring failed on rootfs
Logical volume "snap1" created

then

sudo xbps-reconfigure -f linux4.19
linux4.19: configuring ...
Executing post-install kernel hook: 20-dracut ...
Executing post-install kernel hook: 50-grub ...
Generating grub configuration file ...
grub-probe: error:unknown filesystem.
/usr/bin/grub-prob: error unknown filesystem
Found Void on /dev/mapper/linuxvg-snap1
done

With a reboot, I end up with blank screen...

My fstab:

cat /etc/fstab 
UUID=de2e2df6-595d-4f8e-9537-a03459113cbd / ext4 defaults 0 1
UUID=3C5D-89E5 /boot/efi vfat defaults 0 2
tmpfs /tmp tmpfs defaults,nosuid,nodev 0 0

and grub-config:

#
# Configuration file for GRUB.
#
GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=false
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="Void"
GRUB_CMDLINE_LINUX_DEFAULT="loglevel=4 slub_debug=P page_poison=1 net.ifnames=0"
# Uncomment to use basic console
#GRUB_TERMINAL_INPUT="console"
# Uncomment to disable graphical terminal
#GRUB_TERMINAL_OUTPUT=console
#GRUB_BACKGROUND=/usr/share/void-artwork/splash.png
#GRUB_GFXMODE=1920x1080x32
#GRUB_DISABLE_LINUX_UUID=true
#GRUB_DISABLE_RECOVERY=true
# Uncomment and set to the desired menu colors. Used by normal and wallpaper
# modes only. Entries specified as foreground/background.
#GRUB_COLOR_NORMAL="light-blue/black"
#GRUB_COLOR_HIGHLIGHT="light-cyan/blue"

and lvm.conf: http://0x0.st/zo2u.txt

Edit: I have lost my irc nick, so can't join there