Intel Raid w/Optane (usually what you are referring to) is completely unsupported in any Linux distribution, so it will never work. Really nothing more to discuss.
The only raids you can have on Linux are:
- MD Raids (software), built into the kernel.
- Hardware Controller Raids for supported controllers. (For servers.)
- Raids created via certain filesystems like LVM (really #1 with another layer), BTRFS/ZFS
If you're already installed Windows into that raid, you have to go into your bios and turn it off by switching on AHCI mode on the disks. After that you go back and reinstall the Windows, then the Ubuntu. If you want to configure a soft-raid (aka #1) you have to use the Ubuntu Server installer and go through the steps. If you are new to Ubuntu, which I presume you are by asking that question, then you likely will not be very comfortable with the text mode installer that the Ubuntu Server gives you. You will have to partition the raid by hand even in that installer and know what you're doing or you won't get it to work. Probably not something to do if this is your only computer or your first time around.
There is no workaround for the "Intel Raid" situation presently, but back in the day there used to be a Phoenix raid bios that used to work because it emulated the software of an actual raid controller and it worked. That was only available for AMD platforms back in the day, however. Anyway, that was the only time it ever worked. I'd imagine it still works if you had that hardware, but otherwise it just doesn't. :D
