One alternative for those who don't want any of the major NAS vendors, just use RHEL10. It's free up to 16 licenses, it's ultra stable, cockpit is a very mature gui for a lot of maintenance tasks.
It's a set and forget OS that will run for years without requiring your attention. But these days it has decent container support for hosting services on.
Or rocky, which is a 1:1 clone of RHEL that doesn't require licenses. https://rockylinux.org/
The problem with RHEL is that the free version exists at the sufferance of IBM, a company not well known for being motivated by keeping tech enthusiasts happy. I would use Debian, personally. Not as long of a support cycle as RHEL, but still quite stable and no possibility of corporate rug-pulls.