No Bootable Device after installing Ubuntu 20.4?

Question

ubuntu

I installed Ubuntu, before that it was Windows 10.
After installation, rebooted, a message appeared that I needed to disconnect the USB flash drive, turned it off, then I get the message No Bootable Device.
Further following the answer from this question: Why won't ubuntu start after installation? , I do according to the first instruction from this site https://help.ubuntu.ru/wiki/%D0%B2%D0%BE%D1%81%D1%... Executed

: sudo fdisk -l
Got:
Start device End Sectors Size Type
/dev/sda1 2048 976895 974848 476M EFI
/dev/sda2 976896 40038399 39061504 18.6G Linux file system
/dev/sda3 40038400 250068991 210030592 100.2G Linux file system

Ran: sudo mount /dev/sda1 /mnt
Then: sudo grub-install --root-directory=/mnt /dev/sda
Got:
Installing for i386-pc platform.
grub-install: warning: GPT partition label has no BIOS Boot Partition; embedding is not possible.
grub-install: warning: Embedding is not possible. Given the options, GRUB can only be installed using blocklists. However, the block list is an UNRELIABLE mechanism and should not be used.
grub-install: error: will not continue with blocklists.

BIOS is set to boot from SSD.
I'm not strong in Linux, tell me how to fix the problem.

Acer Aspire laptop

Answer 1

The solution was found here
www.decker.su/2016/07/ubuntu-on-acer-aspire-es-11-...

Answer 2

First you need to find out if the computer is running in BIOS or UEFI mode.
Under your link it is written "which addresses BIOS"; I have a feeling that this instruction may not work with UEFI.
Judging by the presence of the section
Also, I'm not sure what sudo mount /dev/sda1 /mntis correct. Because you have EFI in sda1, and Linux root/boot system in sda2 or sda3.
Google "grub-install blocklists" - you probably need to specify some options for it to use it.