For formats that support the embedded definition of field domains (currently GPKG and GDB), QGIS automatically converts the embedded field domain over to the equivalent QGIS editor configuration for the field.
This means that GPKG/GDB with coded field domains will automatically load into QGIS with their correct Value Map widget configuration intact, so that users see descriptions for field values instead of raw codes. Fields with a range (min/max) type domain will be translated to the range widget for the field as well.