Dual booting Windows 10 and Ubuntu 20.04 - with RST issue fixed

Disclaimer: Steps after taking ISO image can quite vary with respect to the laptop that you use. This blog helps best for the ones using Acer Aspire 7 (i5, 9th gen)
Caution: not a very big tech-freak, more of a story-teller 😁

Fix the Turn off RST right away
Why Ubuntu/Linux?
If you are a person who's fed up of downloading millions of stuffs from different sources for a software and still facing errors like something's missing or a person who's lazy enough to move your mouse around, Linux OS would be better for you 😏

Preferable Pre-requisites:

• 4+ GB RAM
• If Windows 10 is pre-installed, you do not need to worry if Linux can be dual-booted in your system. It surely can.
• 30+ GB of continuous free space to spare. (Preferably 60+ GB if you are going to use Linux regularly)
• A USB of 4+ GB capacity for storing Ubuntu ISO file for dual booting

So, all the best and let's begin

Step 0: Back up everything (optional) - I didn't though

Step 1: Download the ISO image of Ubuntu.

By default it gets downloaded into Software in C:/ though it doesn't matter much where it gets downloaded.

While you're at it, let's make a bootable USB

Step 2: Making a bootable/live USB

Even though I used Universal USB Installer for creating a bootable USB, there are other software too like Rufus and UNetbootin which might require a download.

Plug in your USB.

In UUI, clicking on the "Download UUI" will bring up a new tab and choose your file location to save it. Go to the location where you have the file and follow:

Select your installed Linux Distribution, in this case, Ubuntu
and browse-select its ISO file.

Now, choose the USB which is to be made bootable and format it if you wished to. I didn't though, because I had enough space for Ubuntu ISO File too.

Click on CREATE and you hold a bootable USB in your hand now.

Step 3: Shrink and create space for Ubuntu

For that, open Disk Management and right click on C:
P.S. : I took this screen print months after dualbooting Ubuntu

Choose Shrink Volume...
A window with the image as a part of it pops up. Ideally, type in 20000

As the process gets completed you'll find unallocated space and that's where Ubuntu will live.

Step 4: Boot into Ubuntu and see if there's an issue due to RST in your system.

Find Boot Sequence Key. For Acer Laptops, it's F12 .

Reboot your system with USB plugged in and continuously press F12 . Choose Ubuntu and wait till it loads.
A page like this will be loaded.

But when you try to Install Ubuntu you'll get this screen...

So, yep... That's the whole reason I'm writing this. Also, I'm just a beginner and not much exposed to the words like UEFI/Legacy, SATA- AHCI/RAID/IDE and all. So, until I learn about them, all I can do is type out a solution that worked, without wiping off the pre-installed Windows 10
Anyway, click on the restart option and get back into Windows.

Step 5 Fixing the issue

In Windows, open up command prompt as an administrator (Run as administrator) and type in

bcdedit /set {current} safeboot minimal

Find your BIOS setup key. For Acer Laptops it's F2 .
Reboot your system with USB plugged in and continuously press F2
It should take you to BIOS setup.
In my laptop, pressing Ctrl + S in Main tab listed every advanced options.

On the information page itself new rows get added and search for SATA mode and change it to AHCI instead of RAID (or in rare cases, IDE)

For some of non-Acer laptops, this option is named as Storage in Configuration tab.

A frightening question will be asked,

All existing data stored on the drives will be erased when resetting the controller mode. Do you want to proceed? [Yes] [No]

Don't worry, nothing will happen. Select YES
Press F10 and come out of BIOS and you will be automatically taken to safe boot mode. This just ensures that your Windows is okay to proceed with dual booting.
Open Command Prompt and press enter after typing in

bcdedit /deletevalue {current} safeboot

Step 6: Setting Sails

Restart the system and now, choose Ubuntu from the boot menu (or Try Ubuntu, if it exists).

I followed this site for rest of the steps and VOILA, your Ubuntu is ready to use

Not gonna lie: A 50+ clicks and tiring setups on Windows while software installation is replaced by just a single line on Terminal Window, sudo apt install ___
Good Luck! Keep Learning

Courtesy: My tech-freak dad, loads and loads of websites, YouTube tutorials and two whole days