What would be a preview provider? Can collabora act as one? Are there possible missing dependencies in the docker container from the AppCenter version?
unfortunately i can’t answer any of these questions as i don’t have any knowledge about that. Just have seen the changelog entry while reading the changelog before updating my own ownCloud installation.
But i guess this just means that no provider is available for this specific document you’re trying to preview. Maybe you can find some notes on this in the ownCloud documentation?
yes i had found this fix and linked it previously. But if i understand it correctly that this only fixes the shown image if no “Preview provider” (whatever this is?) is available.
But i think @denissen is probably more interesting in making such a “Preview provider” available within the appliance so that a preview is shown or am i wrong?
Older versions of ownCloud also supported the preview generation of other file types such as PDF, SVG or various office documents. Due to security concerns those providers have been disabled by default and are considered unsupported. While those providers are still available, we discourage enabling them, and they are not documented.
i don’t think that the app update won’t solve your initial issue about missing previews / thumbnails for documents. From what i understand the appliance just doesn’t provide / have configured the required preview providers to show previews / thumbnails for documents.
Even if the update does not solve the problem of missing previews for files other than image files, at least we won’t see the “image not found”-image any longer