Why is the BIOS not detecting the hard drive where is Ubuntu installed

bootdual-bootgrub2hard drive

I have an acer travel mate laptop with windows and I wanted to also have Ubuntu, so I downloaded the 22.04.3 image and used rufus to make a booteable USB. Then I proceed with the instalation in one of my hard drives, I have two (one for Windows and other for Ubuntu). I manually create the partitions /boot, swap, / and /home and everything is fine. Then I restart the laptop and instead of loading me into grub to select he required OS it keeps loading Windows 10. I thought that it was the boot priority in the BIOS and then I noticed it, the hard drive where I installed Ubuntu is not in the boot priority. My main drive (Windows) is the Gigabyte one and the Toshiba is for Ubuntu. Here is a picture:
enter image description here

How can I make recognizable the drive?

Edit
I have made some discoveries. If the bios mode is changed to legacy, the Toshiba disk appears in the boot priority list:
The boot priority menu
But it is not detected by the boot manager:
The boot manager legacy mode
If the bios is in UEFI mode, the boot manager only detects the windows partition:
the boot manager in UEFI mode

Also,I tried to reinstall ubuntu and this where the partitions detected:
enter image description here
You can see that the EFI partition is VFAT i don't know why because it was fat32 when I installed it for the firs time. And this is how I left it:
enter image description here

Best Answer

I managed to solve it, but I am not sure of what I have done. Here are the steps:

  1. Instead of installing ubuntu I used kubuntu (I supose that you can use ubuntu).
  2. Put the bios in legacy mode. It is posible that this is not necesary but it worked for me because in UEFI mode the disk where Kubuntu is installed was not being detected.
  3. In the part of manual partition put the EFI partition FIRST. I think that is here where I screwed up.

And that is all.

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