Customize Scheme Handler

create a desktop entry [name].desktop in ~/.local/share/applications/. More information about desktop entries

[Desktop Entry]
Type=Application
Name=[description]
Exec=[program] %u
StartupNotify=false
MimeType=x-scheme-handler/[scheme name];

Then setup mime information

xdg-mime default [name].desktop x-scheme-handler/[scheme name]

# check if set up correctly
xdg-mime query default x-scheme-handler/[scheme name]

# may not be necessary?
update-desktop-database ~/.local/share/applications/

# test
xdg-open [scheme name]://something