I have to use gsettings from /opt so that ubuntu maintainers will accept my application.
I may not use /usr or any of the underlying directories so /usr/share/glib-2.0/schemas is not an option.
Did you try quickly?
quickly package --extras
This will use the /opt directory.
I solved this by creating a wrapper script :
GSETTINGS_SCHEMA_DIR=~/.local/share/glib-2.0/schemas /opt/my_app_dir/my_app