Install Ubuntu 18.04 along Windows 10 on Dell Inspiron 3xxx

This is a log of my efforts to install Ubuntu 18.04 along Win10 on a Dell laptop.

It doesn't serve as a guide but more as a debugging log.

It started easy. Burn an ISO image using Rufus. Remember to select GPT (not MBR as the default) on later computer models.

Partitioning the hard drive following the steps in https://itsfoss.com/install-ubuntu-1404-dual-boot-mode-windows-8-81-uefi/ .(Same as many other guides, no issues).

In the process, I have disabled BitLocker (at Windows search, type bitlocker and Turn Off encryption. This may take awhile depending on the number of files on the hard drive).

I also disabled Secure Boot. This is done in BIOS menu. It can be accessed at start-up by pressing F12->BIOS->Secure Boot.

If Secure Boot is deactivated but BitLocker remained on, the Windows booting sequence will halt and ask for Recovery Key. I didn't give it the key as I was afraid it might reactivate the functionalities that I just disabled.

 The first major problem is that there is no option to boot from a USB stick at the boot menu (after pressing F12). 

 The first working solution is found in the answer here by creating a booting option manual:
https://askubuntu.com/questions/726938/how-to-boot-from-a-usb-in-uefi-mode-on-a-dell-inspiron#
The names of the files in Step 5 are different for me. I tried both the file with all capitalized names worked for me. Also I had to make sure that it did not have Secure Boot.

The second major problem is that the installer cannot access the partition I recently created. An identical image is seen in the question here:

https://askubuntu.com/questions/1041305/ubuntu-16-04-cant-see-my-ssd-partitions-when-installing-alongside-windows-10

The solution is to follow the second approach in the first answer exactly as the post suggested.

Now we can return to the steps in https://itsfoss.com/install-ubuntu-1404-dual-boot-mode-windows-8-81-uefi/ to finish the installation.

The last difference in my installation is that the default ubuntu booting option doesn't work. It leads to some kind of system recovery assistant because it can't find the boot files. So I again created a booting option manually, just like the steps in https://askubuntu.com/questions/726938/how-to-boot-from-a-usb-in-uefi-mode-on-a-dell-inspiron#, except that in Step 5.3, I chose another partition instead of FS0 and tried a booting file in the EFI directory. I think I selected the one starting with sh* since it is secure boot. 

I have not changed any settings in Windows back to what they were. So far my system hasn't crashed yet. I will follow up if I receive any surprises.

Some more reference:

[Installing Ubuntu on UEFI systems] 
https://help.ubuntu.com/community/UEFI