To create such a graph you will need to wrangle the data. A technique to do this is called scaffolding where you join a date field to fill in the dates between your start and end for each order, thereby creating duplicate rows of data. You must ensure you set a condition where the new date is greater than the start and smaller than the end.
I highly recommend you do this with prep and watch this video to help you do so: Solving tough time-based problems with skeleton tables and Tableau Prep - YouTube
Scaffolding is only necessary for ticket counting if your row data is sparse compared to your bins. In this case we can use Custom SQL to set a counter whose running sum will be the number of open tickets in any month.
SELECT [ActiveOrders#csv].[Start] AS [Date], +1 as [Count]
SELECT [ActiveOrders#csv].[End] AS [Date], -1 as [Count]
Custom SQL for files is only available if you select Windows legacy connection when opening them but if you're source data is in a database you won't have that limitation. I exported the Hyper data to a CSV and opened that.
I also added a table filter instead of a regular date filter so you can set your date range without messing up your running sum. See 10.4 TWBX attached. You won't be able to edit the data source unless you put the attached CSV somewhere you can access from Windows. The second date filter excludes nulls in order to handle tickets that are still open so as to not decrement the count.
Thanks for clarifying. I tend to avoid recommending the use of custom SQL because it has a high impact on dashboard performance. It is always better to provide Tableau with a data set that is ready for analysis, and push back such manipulations back to the data source level.