This is really not ok. WTF.

To be fair, that bios-managed RAID is still using a hardware controller. It’s embedded in the motherboard.

Anyway, hardware RAID is discouraged in home/workstation environments as you don’t have control over how the controller implements it. So if the board breaks, it’s harder to retrieve your data.

Linux has support for real software RAID, for example using LVM or filesystems that have that feature. It’s easier to setup than it may sound. Most distributions can enable that during installation of the OS.