Dual Boot Windows 10 and Kubuntu - SATA AHCI vs RAID [error]

I dual installed Kubuntu on a computer with Windows 10, grub is on /dev/sda while the Windows boot manager is on /nvmesomethingsomething.

To install it, I had to set SATA from RAID to AHCI in the UEFI BIOS Setup. With SATA AHCI the boot of Kubuntu works. But when I try to boot into Windows, I get a BSOD with INACCESSIBLE_BOOT_DEVICE.

If in UEFI, and I select RAID instead of AHCI, I can boot into Windows, but Kubuntu's boot process results in me ending up in an initramfs terminal.

So I can get only one or the other, but never both working systems.
Is there any solution?

Probably you have to update your bootmanager, because, it points to disappearing path, that is:

• when Windows was installed in RAID mode, thus the bootmanager point to /nvme but when you switch to AHCI /nvme is destroyed and replaced by something else.
• in the same way, when you installed Kubuntu in AHCI mode, it was installed on /dev/sda but when you switch back to RAID, it is destroyed.

OT: why did you need to install Kubuntu without RAID?