QGIS 3 does not load default styles from spatialite (defined in QGIS 2.18)

On the second look the changes seem to be less drastic. I noticed the query for styles related to the layer referred to in the Error message is output on the Log Messages | General Tab as a Warning:

SELECT id,styleName,description FROM layer_styles WHERE f_table_schema=NULL AND t_table_name='my_table' AND f_geometry_column = 'geometry' ORDER BY useasdefault DEC, update_time DESC

apart from the above layer_styles table not having an id column but OGC_FID (this is easily fixed and fixes the above error), the query seems to be wrong in f_table_schema=NULL wich is f_table_schema IS NULL. One may test this with QGIS DB Manager: Using ...=NULL delivers no results (and does not throw an error), using ...IS NULL delivers the desired result. As a consequence, no default style is found and loaded.

Issue: https://issues.qgis.org/issues/19426