I use this solution to display actual QDateTime value with milliseconds in a temporary memory layer. And I use another solution to export as CSV the value including the millisecond value.

But then, I realized that "Use Date/Time" option changed the type of the time_break field from QDateTime to string when I exported as GeoPackage. But I need a datetime field in the GeoPackage.

Export using "Use Date/Time" option:

Result (converted to string):

If I don't use "Use Date/Time" option, it exports the field as QDateTime, but it changes all millisecond values to zero:

How can I export it as a GeoPackage to contain the datetime field with the actual millisecond value?

I use this solution to display actual QDateTime value with milliseconds in a temporary memory layer. And I use another solution to export as CSV the value including the millisecond value.

But then, I realized that "Use Date/Time" option changed the type of the time_break field from QDateTime to string when I exported as GeoPackage. But I need a datetime field in the GeoPackage.

Export using "Use Date/Time" option:

Result (converted to string):

If I don't use "Use Date/Time" option, it exports the field as QDateTime, but it changes all millisecond values to zero:

How can I export it as a GeoPackage to contain the datetime field with the actual millisecond value?