@NiwlCraft In my opinion you want to look for something that runs mainline Linux. Which for arm boards is as rare as water in the desert.

@portaloffreedom @NiwlCraft postmarketos (read: Linux) runs on quite a few arm devices:

https://wiki.postmarketos.org/wiki/Devices

Devices - postmarketOS Wiki

@gim @NiwlCraft I know about it but I never throught of using postmarketos to run a NAS.
Looking at the supported devices page I mostly see phones and tablets.