So, first time into Ubuntu. I have been trying for the past few days to get this to work, but couldn't. That's the problem:
Successfully installed Ubuntu, all good. My PC restarted and got into the Grub Menu (I also checked BIOS and UEFI boot order settings, Ubuntu was first, HOWEVER, there was NO Windows Boot Manager in the boot order at all! I ignored that since everything was ok) My PC booted to Ubuntu, so when I wanted to go back to Windows 10, I rebooted, and selected from the GRUB menu Windows Boot Manager.
HOWEVER, when I went back to switch to Ubuntu, there was NO GRUB menu. It was like I never installed Ubuntu. It just booted straight to Windows 10.
Checked UEFI and BIOS. The "Ubuntu" was completelyreplaced by Windows Boot Manager.
What's up with that?!?! I have been trying everything all day! Ubuntu is still installed but I just can't access it?!?! I tried with commands to download again GRUB (repair), but even if it said it completed, nothing happended.
My computer is pretty old, pre built from 2012 I think, HP 6300 Pro Micro tower, Core i5-3470, 16GB DDR3 RAM, GTX 1630. All of my SSDs are GPT, including the bootable media used to install Ubuntu. Windows was installed in UEFI mode.
P.S: The partition I had for Ubuntu was 35GB, I think it's ok, right?
EDIT: (extra info) Fast Startup was ALWAYS disabled. Ubuntu was installed in UEFI mode, my PC's ''BIOS Mode'' is set to UEFI. In addition, since my question is marked as duplicate, i want to clarify , that in my case, GRUB was ok, and in general, everything was ok. However , things started to get weird at the first time of booting into Windows after installing Ubuntu. Also, i have tried to see the boot entries using the bcdedit command in cmd, but the only the Windows Boot Manager was there.
EDIT 2, VERY IMPORTANT!
So, i tried entering the UEFI settings as usual. Windows Updates>Recovery>Advanced setup>Advanced options>UEFI settings.
HOWEVER , that was the only time i got the option to boot from another OS (see picture below). That is the only time i see this menu. However, even after i selected Ubuntu it still (for some reason?!) booted into Windows 10.
(the picture is in Greek language but i think it's obvious to understand what it says) Here the OS selector
Left side, at the bottom it says "Use of other system"
Please someone help! Can't get this figured out....!