I am aware of a series of related questions and solutions, but I am about to try them all without success.
Recently, I updated SSD on my Dell XPS 13 and expected to go to dual boot configuration. I started with the installation of Windows 10; There were some problems, I was not detecting the new SSD. I have read somewhere that I should change the SATA operation in BIOS from RAID ON to AHCI. I did it and installed Windows without any other problems. I reduced the Windows partition and left 50 GB of unallocated space. Then I downloaded Ubuntu, made a bootable USB with Rufus and tried to install it.
Here is my problem in a nutshell. I can't install Ubuntu from USB: Ubuntu starts the USB, but when I try to install it, it doesn't detect my SSD. The solution to this that seems to work for other people is to change from RAID ON to AHCI, but I have already done so. I also checked the Windows Device Manager storage drivers and in fact it is what it is supposed to be (according to this: https://askubuntu.com/a/1127531/1006012).
I also did all kinds of related things in the BIOS: enable usb boot, disable safe boot, change Fastboot to Thorough, etc. I have also disabled Fastboot in Windows Power Options and made sure it is not hibernating, that seems to block the drive in some way.
I also tried using different ports for my USB adapter (all are USB-C but 2 of them are also Thunderbolt3).
If anyone has an idea of how I can fix it, I would be very grateful.