I'd go for an
action log. It's almost the same thing, but notifications imply ephemeral pokes about some of the stuff that happened, mixed with engagement boosting spam - there's a lot of unpredictability embedded in this concept, as the app is usually trying to guess what you may (or it thinks you should) find relevant.
An action/activity log is just a reverse-chonological log of things that happened. You could make one by recording every would-be toast and putting it on that list, complete with a timestamp, and any of the context-relevant action buttons (like "undo", or "view item", etc.). The list should be a fixed recording[0], without any way to dismiss some or all of the entries. Add some attention-grabbing indicator whenever something is added there, and you get all the benefits of toasts with none of the drawbacks: the log lets you report completion of optimistically-executed actions, provide place for context-relevant buttons, and also is accessible, can be browsed at uses' own time, improves discoverability and learning, and can be upgraded to also enable undo feature.
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[0] - Well, appended from top, and possibly unwinded by undo. Users understand that. Can't be append-only, because mixing that with undo gives you the undo system from Emacs - very powerful but also nearly incomprehensible to most people.