Very limited: as soon as you have cleared a notification it is gone forever and old notifications are also gone rather quickly.
https://www.lifewire.com/iphone-notification-history-1189516...
https://www.lifewire.com/iphone-notification-history-1189516...
1: you can't get access to actions or details in the history (e.g. no long-press to change settings), nor does it show you ones you didn't dismiss by hand afaict (I've been having Discord notifications disappearing almost immediately after making a noise, but there's nothing in history even though I saw it for its whole half-second existence because it popped over my screen).