I just fresh installed KDE neon on my laptop Acer Aspire 3 and I notice when booting up I always have to select an OS to boot.
Choices are
KDE neon GNU/…
Windows bootloader
UEFI firmware…
Grub???
I have a windows 10 installed in other drive btw.
I already configure the boot order in bios but it does not work.
Can’t seem to find any solution online that work so I resort to asking question here.
It depends slightly on your Linux version.
The terms you want to google for are “grub default”. The grub boot loader is the thing which handles the initial booting on most linux and dualboot systems.
There is a good explanation about grub configurations at How do I set the grub timeout and the grub default boot entry? - Ask Ubuntu
yes I just found out it was grub boot loader menu but I don not want that appearing each time I booted my system.
also Im not dual booting
actually I tried every solution in every thread I could find but it did not work
what I have done so far:
set GRUB_TIMEOUT=0
etc. anything related to grub files including setting recordfail to grub time out
and ofcourse i needed to sudo update-grub after that
I even installed grub customizer and deleted some selection that I dont want.
check the boot order in my BIOS.
and the menu still appear when booting up.
btw setting grub timeout to 0 takes me to grub command prompt
Idk what to do at that point but what I did was fresh installed the os.
what solved my issue was
I remember there is “another” hardrive in my laptop with windows 10 installed so
I removed my windows 10 hard drive before installing linux to a new drive.
after installation I repeatedly boot my system to check if the grub menu will appear and its gone
then I put back my drive with windows 10.
now it boot directly to linux which is want I want 
I think it has something to do with grub/os-probe it detected that I have another bootable OS in my other drive while installing linux.
So lesson learn, remove any drive that has bootable OS when installing new OS to a new drive.
Yes, if you had another bootable drive installed in your system when you installed (linux) grub and then removed that bootable drive, grub will detect that something has unexpectedly changed. Grub will then automatically open the grub menu even if you turned it off by default.