Compare the two filesystem views
A folder existing on the host does not automatically make it visible inside a container. If Jellyfin’s library picker cannot find a known host directory, identify the media mount’s source and target before changing the library type or renaming the films. The host’s path and the path visible to the server process are different locations in that arrangement.
Use the publisher’s mount structure
Jellyfin’s container guide separately mounts persistent configuration and cache data and binds media folders into the container. Its migration examples preserve media paths expected by an existing configuration. Read-only media mounts are also supported. A working configuration volume therefore does not establish that a media folder was mounted, or that the server has filesystem rights to change its contents.
Check a harmless sample before importing a whole collection
For example, an administrator may expose a host collection at a chosen container path, then select that server-visible target in the library. Inspect one authorised sample and confirm the intended permissions before adding a large archive. Preserve existing configuration and mount information during a migration; changing several paths at once makes missing-item results difficult to interpret. Do not create empty substitute folders merely to make a path picker accept a name. If the content remains absent, record the host-to-container mapping and server-visible path privately, with personal paths and access credentials removed from any public report.
Questions, answered
Does mounting configuration automatically expose the media folder?
No. Jellyfin’s examples use separate configuration, cache and media mounts.