You don't want hardware raid. Some options you can research:
Mdadm - Linux software raid
ZFS - Combo raid and filesystem
Btrfs - A filesystem that can also do raid things
Some OS options to consider:
Debian - good if you want to learn to do everything yourself
Truenas Scale - Comercial NAS OS. I bit of work to get started, but very stable once going.
Unraid - Enthusiast focused NAS OS. Not as stable as Truenas, but easier to get started and a lot of community support.
There are probably other software/OS's to consider, but those are the ones I have any experience with. I personally use ZFS on Truenas with a lot of help from this YouTube channel. https://youtube.com/@lawrencesystems?si=O1Z4BuEjogjdsslF