I cannot get Nextcloud to show thumbnails for any video files. I have installed or already have the latest ffmpeg, imagick, ffmpeg thumbnailer. I cannot use the preview generator app because I use encryption, but that should not affect the ability to generate thumbnails. As far as I understand, that only helps with load times. I cannot get an actual thumbnail for videos to begin with. I am not sure if I should be looking to my OS or at Nextcloud for the answer.
I am on Ubuntu 18.04 Server updated with all the latest (apache2, php, etc)