I started using django-simple-history in order to keep the history but when I delete an object (from admin page at least) I notice that it is gone for good.
I suppose I could create tags and "hide" objects instead of deleting in my views but would be nice if there is an easier way with django-simple-history, which would also cover admin operations.
When objects are deleted, that deletion is also recorded in history. The object does not exist anymore, but its history is safe.
If you browse your database, you should find a table named:
[app_name]_history[model_name]
It contains a line with the last state of the object. That line also contains additional columns: history_id, history_change_reason, history_date, history_type. For a deletion, history_type will be set to "-" (minus sign).
Knowing that, it is possible to revert a deletion programmatically, but not through the Django Admin. Have a look at django-simple-history documentation for details on how to do it programmatically.
Hope that helps!