You can’t hard link across docker volumes. In the second example, you need to remove the /media/movies and /media/downloads volumes, only keep /media.
After fixing this, only future downloads will be hard links. Use a deduplication tool like jdupes to create hard links for the already downloaded files.
If you don’t want to be on the bleeding edge and want a distro with longer support, CentOS Stream isn’t bad. Sure, there was some controversy surrounding it, when Red Hat killed the old CentOS. But ignoring that, the distro itself is pretty good and stable.