I think a concept of archival rather than direct deletion is a good concept. Items shouldn’t be directly deleted and can only be archived. Archiving an item will gather all such items under an “Archived Items” list that can be either global to the instance (or later, under a “space” within the instance).
Archived items can be deleted permanently by user or can be deleted after x months as per admin preference. Archived items should be “restorable” in future (this will require much the same work as “undo” of delete otherwise planned now).
This archive concept is much like what’s there in Trello.