"No bootable device found" after uninstalling Windows 10 on dual-boot Ubuntu 16

1. I was deleting my Windows 10 from my dual-boot Ubuntu 16 LTS using OS Uninstaller from a Ubuntu live-usb.
2. When I deleted the Windows, OS Uninstaller detected some error but unfortunately I did not take note of it.
3. After that I try to boot into my Ubuntu but it says "No Bootable device found"
4. Tried to follow steps on IFOSS
5. Found out that I have nothing to select on this
6. The next thing I do is booting from live-usb again and install boot-repair package to repair my installed Ubuntu but got some error says
7. I cannot read what on Gparted means but here is what it looks

I want to re-arrange my partition so it looks clean and be able to boot into my Ubuntu again, thank you in advance!

2 Answers

First, the prompt by Boot Repair to create a BIOS Boot Partition means that it probably booted (that time) in BIOS/CSM/legacy mode; however, both your Windows and your Ubuntu were installed in EFI/UEFI mode. Mixing the two boot modes is often possible, but usually very awkward, and should generally be avoided. To avoid this problem, you should disable the CSM in your firmware, if possible. See this page of mine for more on this issue.

Beyond that, EFI boot loaders are stored on the EFI System Partition (ESP), which is a FAT partition with a specific type code. Your /dev/sda2 has the ESP type code, but appears to use NTFS, and does not seem to hold any EFI boot loaders. My guess is that you've accidentally wiped out a formerly-valid ESP, thus destroying your Ubuntu boot loader. Your easiest path to recovery is:

1. As noted above, disable your CSM, if possible. If you can't figure this out, at least learn to control your boot mode, so that you boot whatever system you use to launch Boot Repair in EFI mode rather than in BIOS mode. (FWIW, your BootInfo output was from an EFI-mode boot.)
2. Using an emergency system, convert /dev/sda2 to FAT. (Use GParted or mkdosfs for this task.)
3. Run Boot Repair and tell it to fix the Ubuntu installation. Alternatively, you could install another boot loader, such as my rEFInd boot manager; but Boot Repair is likely to be easier in your case because you seem to have Secure Boot active. I'd therefore hold rEFInd as a backup option in case you have problems restoring GRUB.

Another option, which you might want to give serious consideration, is to use your emergency recovery system to back up all your user data from the disk, delete all the disk's partitions, do a fresh install of Ubuntu, and then restore your personal data. This would have the advantage of consolidating your many partitions. If you intend to run this computer with Ubuntu only, having NTFS on the disk is a Bad Idea, since there are no good NTFS maintenance tools for Ubuntu. Thus, when (note: when, not if) an NTFS partition needs repair, you'll have to jump through awkward hoops to do so if you leave those NTFS partitions as they are. On a Linux-only system, you should store your data on Linux-native filesystems, not on NTFS.

I deleted all of my partition except one that contains my data. Solved.