Unable to multi-boot OS WIN10 and Linux

[bushy3]

I have done this multiple times with HP computers but never had this experience.  Typically I boot a lINUX OS from a flash drive , partition the Hard or SSD Drive, install Linux on the new partition and install GRUB for the boot loader.  The BIOS on this laptop seems to prevent this from occurring.  I have defeated Secure boot and installed GRUB and watched as GRUB recognized both Operating System.  All seemed good but upon reboot no GRUB menu is displayed the laptop boots directly into WIN10.  BTW it's WIN10-S.  I created a tedious work around but hope for a simpler solution as I am doing this for an older retirere .  My work around is as follow.  In SETUP i delayed Startup by 5 seconds, hit the ESC key during the wait period, choose F9 from the displayed options and then select Ubuntu to complete the startup process.  Afterwards it boots to the Grub menu and I can then select either WIN10 or Linux.

So my question is there anything I can do so at boot so I go directly to the Grub menu?

[WAWood]

@bushy3

Lots of folks are reporting problems trying to install a different OS on a PC that is Win10 S -- and NONE of them have reported any success in doing that.

Sorry, but it's looking like MS has locked these up to FORCE folks into using only Win 10 S (Surprise! Surprise!)

[bushy3]

Well,  I have it working, I can boot into either OS, it's just that my way is cumbersome for a retiree.