Regarding Notepad on Windows 11, NVDA repeating the last line entered is actually a known problem, and a brief discussion between developers indicates that this may have something to do with (once again) a possible bad UI Automation implementation from Microsoft as Narrator suffers from text announcement bug sometimes (this is one of those instances where I just throw my hands up and give up; I spent some time trying to do something to no avail).
As for find dialog in new Notepad, NVDA not announcing things when you press Enter key is the correct behavior - this can also be observed with Narrator.
