Hello everyone. We hope everything is well with you.  Guys, I need some assistance with my computer. The same PC runs Ubuntu 20.04 and Windows 10. Apparently, the grub bootloader disappeared after Windows 10 was updated. I am unable to install the Grub bootloader. I am not an expert in this field. Can anyone provide any suggestions? Any help will be appreciated.

Hello, have you tried following this guide?

https://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd

Where do you get stuck?

Thanks for replying and for the suggestion also. It's helpful. But sorry I can't try the method you mentioned earlier. Although, I figure out the issue after finding this on Google. The issue is fixed after the following command on the Windows command prompt. The command is "bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi". 

So you have grub as secondary loader?