In wayfire edition there are two default video players,
- MPV and
- Celluloid (MPV's frontend)
When I change default player to mpv the videos are opening directly by clickinng videofile icon, and when I changed it to celluloid videos are not opening directly (celluloid not starting). But when I try to play video by first opening celluloid from app list and from it selecting video file then its started working.
So, Celluloid is not starting while chosing it as default player.
MIME (default applications) is a complicated case for the diversity of Linux several DEs and systems.
It seems Wayfire is not so polished for inexperienced users.
You should read about MIME at Archwiki, to see what I mean.
Your user account's MIME settings are in this file:
I would suggest you choose a MIME editor and install it to help you more easily setup your default apps.
Since Wayfire is not based on a major DE like KDE or Gnome which include MIME editing utils, maybe a 3rd party app could be a better solution.
In a quick AUR search, I find this package interesting for this case.
If you decide to install and use it, we would appreciate your feedback.
Or try other utilities.
Or edit your
$HOME/.config/mimeapps.list manually, after reading Archwiki and relevant man pages.
Thank you, I will try to edit this mimeapps.list file.