Ubuntu install hangs at "Installing the 'grub2' package..."

During the installation, there's a way to skip installing grub. Look at the "Device for boot loader installation" dropdown.

Instead of choosing the entire device "/dev/sda", choose the partition you'll install Ubuntu, such as: "/dev/sda1"

If you choose "dev/sda", you're supposed to rewrite the boot record for the entire drive, which I believe is what's your issue is all about.

But when you choose "dev/sda1" (or sda2,sda3...) you get to place the boot flag at the beginning of the partition, not the entire drive. That does not make you go for a change in your bootloader. In other words, you place a boot flag as a "subtitle" to your pre-existing bootloader.

After you apply the fix, if you ever want to switch to Grub2 for any reason, use the Ubuntu Boot Repair disk: Ubuntu Boot Repair

If all else fails, try to "rewrite your MBR" because during your uninstallation of Windows, its boot sector may have accidentally remained there. Since you are doing a fresh install of Ubuntu, this may stand as the final option since there's a small chance that Ubuntu failed to handle your Windows partition's boot flags correctly.

In case you have issue when installing on UEFI BIOS (not sure if this issue is adressed only to Acer Laptops) there is a topic here that helped me solve this issue.

I will copy the commands in case it disappears, but all credit goes to Pueseso from Acer Community forum.

-- Boot Ubuntu Live USB
-- open terminal
sudo -s
ubiquity -b
-- Press Continue testing after installation is over.

--Now we will return to the CLI (  https://wiki.debian.org/GrubEFIReinstall  )

sudo mount /dev/sda2 /mnt #sda2 is the root partition
sudo mkdir /mnt/boot/efi
sudo mount /dev/sda1 /mnt/boot/efi #sda1 is the efi partition
for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt$i; done

modprobe efivars # make sure this is loaded

-- notice the bootx64 file
efibootmgr --verbose

-- We will reinstall grub-install for a 64bit version
apt-get install --reinstall grub-efi-amd64

grub-install —no-nvram —root-directory=/mnt
chroot /mnt
update-grub
cd /boot/efi/EFI
cp -R ubuntu BOOT
cd BOOT
cp grubx64.efi bootx64.efi

-- You are finished, reboot the system.