gio mime application/x-bittorrent gio mime x-scheme-handler/magnet
gio mime x-scheme-handler/magnet deluge.desktop gio mime application/x-bittorrent deluge.desktop
update-mime-database ~/.local/share/mime update-desktop-database ~/.local/share/applications
xdg-mime query default x-scheme-handler/magnet
https://help.gnome.org/admin/system-admin-guide/stable/mime-types-custom-user.html.en