My best guess is there’s a permissions issue with whatever you have the ISO stored on. Try copying the iso to somewhere in your home folder.

Debian because it just works. I am interested in trying NixOS though.

I use systemd mount files instead of fstab, that way I can specify a network dependency in the off chance there’s no network connection. Plus I can have other services like jellyfin depend on that mount file so it starts after the share is available.

None of the above. Native debs/rpms/whatever for desktops, docker images for servers.