grub does not appear to be loading, can select os via boot selection (bios screen)

[usbstick]

Hello,

After installing Ubuntu, the system would just boot to Windows and I didn't get to see grub when starting the system. I am able to boot into Ubuntu by going to the bios screen and selecting any of the options marked in green (including the one labeled Windows Boot Manager 1 above the most bottom one; excluding P3 and P5 which I have stricken through with red). The option marked with blue will boot to Windows.

I installed Ubuntu onto the 1TB Samsung 980, Windows is also installed on this drive. Before installing, I resized my Windows partition using Gparted. The system uses uefi (motherboard: Gigabyte B150-HD3P).



I have tried:

-Holding (right) shift during booting
-Installing grub via terminal

I have two questions:

1. What exactly is happening? Are these boot overrides items which are stored in a list somewhere on the disk? How does this work? In the past, on a different non-uefi system, I have dual booted Ubuntu and Windows, however this was with the MBR.
2. How can I make the system load grub so that I may select the OS I want when booting?

Thank you and best regards.

[tea for one]

Your screenshot suggests that you can boot either both Windows and Ubuntu via the UEFI boot options - so far so good.

You reduced your Windows partition with Gparted and it is generally better to use Windows utilities to manipulate Windows file systems.

Did you run chkdsk within Windows after installing Ubuntu?
When you boot Ubuntu in UEFI mode, you can reach Grub with Esc

As you can boot into Ubuntu (Windows must not be hibernating, encrypted etc.), have you tried

sudo update-grub

Edit: The command above is executed via the terminal

[oldfred]

To see details of UEFI boot entries.
sudo efibootmgr -v
man efibootmgr

Is Ubuntu also in UEFI boot mode?
Is Windows fast start up off, so grub can add Windows to grub menu?