Fix thunar doesn't show image/video thumbnails in xubuntu 18.04
Solution 1:
Every post out there that tries to fix the problem of thumbnails they do the following or something similar
$ killall thunar
$ sudo apt install tumbler tumbler-plugins-extra ffmpegthumbnailer
$ thunar -q
and that's it, they open thunar, and thumbnails magically appears, but the ugly truth is You need to restart your machine.