Well yeah to be honest, I kinda hope that one day we can get something like matrix on top of fediverse and so yeah you are right almost every platform doesnt have direct message e2ee but I was hoping that someday someone can build it for fediverse.
I remember its name (sup) but I don't really see any good updates I am not sure to be honest (https://www.notebookcheck.net/Pixelfed-Loops-and-Sup-Alterna...)