Project which has tasks and the tasks get updated in the timesheet. However, doesn’t create any sales order.

In Odoo 16, when Sales Order Item is set to blank, non-billable hours is reflected in Timesheet.

1) the project must be set as "billable"
and 2) it doesn't matter if a task is chosen in the timesheet entry or not but the task must not "private" (usually you can't connect a private task to a project and can't book times without project, so basically it doesn't matter):

timesheet overview:
The 5 hours here from Anita Oliver, where no Task was chosen, are nevertheless set as "billable hours" in the project, but not the times in the private task: 

attention with subtasks; It seems to not work properly here with billable or not:

if not linked to task ,

link directly to project

Non billable hours are generated when timesheets are saved to manually created tasks in the Project module.