Slow copying to external USB HDD in Kubuntu

Format external HDD in NTFS with default cluster size.

Do not check any additional options like SSD optimization etc.

GParted helps to get rid of "Partition 1 does not start on physical sector boundary." issue.

If using dual boot with Windows, Offline USB drive in Windows Disk Management after use.

lsmod | grep ntfs

findmnt -no FSTYPE /dev/sda1

ntfs3

echo "blacklist ntfs3" | sudo tee /etc/modprobe.d/disable-ntfs3.conf

sudo update-initramfs -u

findmnt -no FSTYPE /dev/sda1

fuseblk // You're using ntfs-3g, which shows up as fuseblk.