I've created a simple flavour on bare 2.3.0 system. When I try to deploy on that same system as a test I get the following stack trace:

Debug info: Objects are are not allowed: SimpleXMLElement
Error code: codingerror
Stack trace:
line 699 of /lib/dml/moodle_database.php: coding_exception thrown
line 650 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->detect_objects()
line 1113 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->normalise_value()
line 1520 of /lib/dml/moodle_database.php: call to mysqli_native_moodle_database->set_field_select()
line 1292 of /lib/moodlelib.php: call to moodle_database->set_field()
line 203 of /local/flavours/ingredient/flavours_ingredient_setting.class.php: call to set_config()
line 189 of /local/flavours/flavours_deployment.class.php: call to flavours_ingredient_setting->deploy_ingredients()
line 62 of /local/flavours/index.php: call to flavours_deployment->deployment_execute()