Since the migration of public shares to Vue enabling Hide download also removes the download permissions. But a hidden download is not the same as a disabled download; a hidden download does not disable the download, but simply removes the option from the UI (as some of the viewer apps (like the PDF viewer) need to actually download the file to be able to show it).

Note that just updating to Nextcloud 31 will not change the behaviour of existing shares. However, any share then marked as Hide download will behave as Prevent download.

If that new behaviour is intended then at least it should be documented to avoid surprises (some file types no longer viewable in public shares if download is hidden) for users coming from previous versions :-)

Related:

• Unify "Hide download" for public share and "Allow download" behavior for user share + provide possibility to configure it #46256
• [Bug]: replace senseless "allow download" option on shareing options with "hide download" #45412