I don’t even know what RAID is, I never used it, or set it up at all. It’s been there. Is it the problem with it? I don’t understand the bitlocker / ahci thing you mentioned, so I am asking. Is there anything I am supposed to do?
Try booting on the live ISO. Then open gparted and create a new GPT partition with gparted using device, create partition table and set to GPT. Then close gparted and run the installer and use erase disc and swap file with ext4.
Take a try in the terminal
Boot the live iso
Open terminal lsblk
Look up the disk you want to edit sudo fdisk /dev/sdx (replace sdx with your findings from lsblk)
now you must tell fdisk what to do
press g then Enter to create a new gpt table
press n then Enter to create a new partition
in the following options use the defaults by pressing enter
(In case it asks to delete a signature, do it)
last time
press w then Enter to write the above changes to disk
Now you can format the newly created partition with sudo mkfs.ext4 /dev/sdx1 (change the x in sdx1 to your findings)
I agree it the drive is probably set in raid mode. I see it recognizes the device as md127. I would be looking in the UEFI bios under Raid and disabled or turned off.