Grub menu still appears on Zorin 17

It really looks as though os-prober is sensing another operating system present. You can check what

sudo os-prober

shows in terminal. If it shows nothing, then see below. If it shows another OS, please relay that information.

If it does detect another OS, it automatically resets the timeout to 10 overriding the Grub File.
You can find the line 32 in (edit) /boot/grub/grub.cfg /etc/grub.d/30_os=prober

adjust_timeout () {
  if [ "$quick_boot" = 1 ] && [ "x${found_other_os}" != "x" ]; then
    cat << EOF
set timeout_style=menu
if [ "\${timeout}" = 0 ]; then
  set timeout=10

You can comment those lines out to fi (should be line 38), save the file, then in terminal run

sudo update-grub

1 Like