Can't get "install alongside windows 10" option during ubuntu installation

[Alphavolk77]

I own a HP Notebook 15-AY503TX which came with DOS.I installed Windows 10 using my flash drive when I received the delivery of my laptop.Now 3 years later I want to install dual boot OS with windows 10 and Ubuntu 18.04.I followed the following steps-:

Step 1:Download ubuntu 18.04 iso file from it's website and etcher software to make the bootable pendrive.

Step 2:Formatted my flash drive using FAT32 as instructed in the tutorial.

Step 3:Shrunk volume of my drive C by 100gb for Ubuntu use as instructed in the tutorial.(My C drive still has enough free space)

Step 4:Used etcher to make the bootable flash drive by mounting the ubuntu iso file on it.

Step 5:Checked that quick startup is off and used chkdsk command to check disk(as recommended on many forums) then I shut down my laptop. 

Step 6:Started the laptop then following the usual steps got to the boot device and selected the flash drive(tried two times,using the one with UEFI and the other option without it but the results were same both time).

Step 7:Started installing ubuntu following the next steps but at last step there wan no option of "Install alongside windows".

I want to keep Windows 10 as well as Ubuntu on my laptop.My Windows 10 is BIOS:Legacy.Secure boot is disabled by default.I have tried everything but I can't get that option to install ubuntu alongside windows 10.Please help me by telling how can I have both OS on my laptop.

[WAWood]

@Alphavolk77 

That's actually a VERY BAD idea to use the "along side" option because it allows the Linux installer to shrink Windows partitions and more often than not, that results in file corruptions in the Windows file system, and because it is corrupted, it will no longer boot, and thus you can't use CHKDSK to fix it.

I'm sorry, but we here are not equipped to provide detailed Linux support.

HP only warranties their PCs for usage with the OS that comes preinstalled. IF you replace that with Linux, or add a Linux OS, then you assume full responsibility for maintaining that -- as HP provides Linux assistance only on Redhat and then only to commercial customers.

The primary "challenge" to using Linux on any HP PC is the availability of Linux drivers. Any hardware that does not work will then range from simple (if there are Linux drivers available) to impossible (if there are NO Linux drivers available) to fix.

Since HP does not provide Linux drivers, your best bet for Linux support is to contact the support forum for the Linux distro you are using -- in this case, the Ubuntu Forums: http://ubuntuforums.org/

Folks on Linux support forums have experience using a variety of machines with Linux and know a lot about driver and installation issues. You will be able to get sound and detailed help there.

Good Luck

[Alphavolk77]

Will using the option "something else" be better where I can resize my partitions by myself.I fear that by doing that I may loose Windows 10 and my other files.

[Lil_Boy_Blue]

Hi

Some guides....
https://ubuntu.com/tutorials/tutorial-install-ubuntu-desktop#1-overview
https://itsfoss.com/install-ubuntu/
https://www.cnet.com/how-to/how-to-install-linux/
https://www.wikihow.com/Install-Ubuntu-Linux

???

Checked that quick startup is off

 BIOS and the W10 options?

NB:  Ubuntu and W10 both work as Secure Boot OS's on GPT Secure Boot.

IF in doubt please ask.