Otherwise, e.g. Synology produces excellent devices, etc.
Sorry but had quite the opposite experience even with the professional lines. The only NAS i trust is a Server (at least HP mini server) and ZFS. Stuff like unraid is for Windows mindsets, i don't trust HW-Raid and i especially don't trust Closedsource Software BS for stuff like that, exceptions are Enterprise stuff like EVA's or NetApp and EMC.
This is how you'd mount a synology array in a Linux server: https://www.synology.com/en-us/knowledgebase/DSM/tutorial/St... - it's basically two terminal commands after all the preparation stuff.
I believe QNAP uses mdraid as well but I haven't had any experience with those.
Yes and that raid destroyed itself many times which btw never happened to me on a self-installed Linux.
I'm sorry you've had the misfortune of encountering such problems.
I've been using Synology/Xpenology (a fork of their GPL bootloader) for 8 years, and it's still going great for me.
Btrfs is on the kernel and just works.
You install it on a USB stick, and the web interface has you up and running within like 2 minutes. The only hard rule is that your parity drives must be as large as or the same size as your data drives, but other than that you’re completely free to add or remove disks one, two, or ten at a time and all it takes is like 3 button clicks.
The community is large so there’s always someone to help should you run into trouble but in general the whole thing is pretty brainless. Click button, server work.