https://docs.xfce.org/xfce/thunar/tumbler

packages to install: tumbler ffmpegthumbnailer

directory to create: mkdir -p $XDG_CONFIG_HOME/tumber

file to copy: cp /etc/xdg/tumbler/tumbler.rc $XDG_CONFIG_HOME/tumbler/

disable the ffmpegthumbnailer in ~/.config/tumbler.rc

ffmpegthumbnailer plugin

[FfmpegThumbnailer] Disabled=true Priority=2 Locations= MaxFileSize=0

remove the -f flag from the Exec key in /usr/share/thumbnailers/

[Thumbnailer Entry] TryExec=ffmpegthumbnailer Exec=ffmpegthumbnailer -i %i -o %o -s %s ...

reboot your system.

(thumbnail cache is located in: ~/.cache/thumbails) ... https://www.youtube.com/watch?v=Wket6uLAQCw