Add an "Ebooks" category in file filters to recognize EPUB, MOBI, and other eBook formats

[aitormendez]

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Is your feature request related to a problem? Please describe.

Currently, Nextcloud does not recognize EPUB files (or other eBook formats like MOBI, FB2, etc.) as a specific file type in the file listing filters. Instead, EPUB files appear as "unknown" or simply as regular files.

This limitation makes it difficult to filter and manage eBooks in Nextcloud, especially for users who store large digital libraries. Right now, users can only filter by "Documents," but EPUBs and other eBooks do not appear in this category.

Describe the solution you'd like

It would be great to introduce a new "Ebooks" category in the file filter section, alongside existing categories like Documents, PDFs, Audio, and Video.

This new category should automatically include file types like:

• application/epub+zip (EPUB)
• application/x-mobipocket-ebook (MOBI)
• application/fb2+xml (FB2)
• application/vnd.comicbook+zip (CBZ)
• application/vnd.comicbook-rar (CBR)

Describe alternatives you've considered

1. Manually tagging files – While Nextcloud allows users to tag files, it does not provide an easy way to filter by MIME type, making this an impractical workaround for large collections.
2. Using third-party apps – Some apps (like EPUB viewers) allow opening eBooks, but they do not modify the way files are categorized in Nextcloud's UI.
3. Editing the database manually – Modifying the MIME type database could work temporarily, but this is not a long-term or sustainable solution, as it could break with updates.

Additional context

Adding an "Ebooks" category would significantly improve file organization for users managing digital libraries, online reading rooms, or personal book collections within Nextcloud.

A potential enhancement could also be to allow users to customize file categories in the settings, so they can define their own file groups based on MIME types.

[susnux]

IMHO this is very specific and I guess many other users will come and request their category to be added.
Yet I think it makes sense to have some customization here, so something I thought about:

Currently we can register MIME types and MIME type aliases (e.g. a lot of files map to "documents").
I think also apps should be able to register their MIME types and be allowed to add categories for them.

This way an ebook reader app can register the category "ebooks" which we would pick up in the files app and show in the filter menu.

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@nextcloud/designers what do you think, should we go:

1. just add ebook category for everyone
2. with this generic approach I mentioned
3. do not need additional categories as ebooks are also just documents.

[marcoambrosini]

I like your idea @susnux, so I would go with option 2.

[lsces]

I'm currently playing with a library of material which is managed via calibre and the current collection is all mobi files, which just get downloaded, so where are we on this. Can I use the 'generic approach'? That several ebook formats exist in my library and I'd like them all to use the same viewer although 'pdf' bridges both the library organisation and the generic file system.
( I've only had nextcloud running for a few days so I'm still finding my feet ;) )