You can build a dedicated NAS fairly inexpensively. If you have an old computer you don’t use anymore that’s a great starting point. I was able to find a micro optiplex at my local used computer store for $99 and it runs great. I originally had it running on a raspberry pi 3 but was having power management issues and needed something a little more powerful.
I would recommend using Samba for your NAS. It’s a free SMB server that lets you access your data on all operating systems. Other Linux computers can mount samba by adding a line to /etc/fstab. On Windows you just go to file explorer and click map network drive.
Qbittorrent doesn’t know where the movie came from. You need to go into Radarr or wherever you got the torrent file to find its source and report it