Not a limit that I know about. But novice users will often run into issues with how Plex is building a music database out of the folder structure and the embedded metadata.
It is not simply a file/folder scraping, like a regular music player usually does.
I recommend you very much to go with https://support.plex.tv/articles/200265296-adding-music-media-from-folders/, particularly if you enable the library option “Prefer local metadata”.
Along the way there may be lurking some snags which can be avoided with careful organization and tagging. See for instance Why are all my Various Artists albums showing as ‘Bob Marley’, despite being properly tagged? - #7 by OttoKerner
When using any kind of *NIX based server, one must be aware that Plex is usually running under its own, dedicated user account, which doesn’t necessarily have always access permissions to all folders and files.
