How to get thumbnails working?

I see thumbnails in the card details for attachments that are images (PNG, JPEG). However, there are no thumbnails generated for PDFs and DOCX files. If I click on the attachments, I see symbol indicating that I should wait but nothing happens.

I use a custom image derived from the wekanteam/wekan image from Docker Hub.

My question is: Is it possible to get the thumbnails and/or full-screen previews for PDFs and other formats by installing further dependencies? FWIW, simply adding libreoffice to the image did non allow Wekan to open DOCX.